Plecos dying! :-(

[Jobro]

Hey folks,

I have very bad news. My plecos are dying.

It all started with a water change round about 40% on thursday. While I was at it, I moved some of the sand the plecos had faned up to a huge mountain in front of their caves away so I would have better vision into their caves again. I noticed one young L333 sitting on a anubia leaf, they usually hide in their caves, but with my L333s it's not too uncommen to see one outside and exploring the tank.

The tank is for growing out 6 L333, 5 L260 and 6 L134. All at about 4-6cm in total size.

The next day I noticed more L333 sitting in the open. Right in the light. They were no longer hiding from the light. I knew something was off. I kept watching for a while and when a young L260 shot through the tank, spinning around uncontrollably, I was really frightened. I did a 50% water change. Before the water change i tested for nitrite: 0.0mg/l. Nothing seemed to change after two hours and so I did another 50% water change. I added additional aeriation. I noticed a lot of very very small white worms sitting on the glas and swimming around as well. There have always been some like those in my tanks. They are so small. And I never had any problems with them up till now. So I wouldn't bother. But now there are soooo many of them in the tank. I knew something must have gone terrribly wrong in this tank since the day before.

I waited some more to see if the water change had any effect. It looked like it got even worse. more and more of the youngsters started to swim uncontrolled against the glas or against each other. There are some endler guppy males as well as some cherry shrimp in the tank. both of them seem to be fine up till today. Nothing to be noticed on them.

I decided to place my bets on those plecos. I would swap them into another, bigger tank with other plecos that are fine and healthy. What if they had a disease and all of the healthy plecos would be infected as well? hmm... I didn't want to think about that. After all waterchanges seemed to be not good enough and the raising numbers of "glasworms" indicated something being terribly wrong in this tank. I came to the conclusion it wouldn't be a sickness of any kind, since all of them had the same signs all at once. It just came to quick for a disease. I assumed a poisoning, so bad that waterchanges couldn't help.

I caught them. poor little fellows. some of them didn''t even try to flee from my hand. some even sucked on to my hand. They were in terrible condition.
Once in the new tank, nothing seemed to have changed.

Sadly I had to leave them alone for the weekend (saturday morning till sunday evening). I hoped they would be fine with "better" water in the bigger tank.

As I just came back home. I found 4 of the 6 L333 dead. It's heartbreaking taking those liveless little bodies out of the tank. the 5 L260 and 6 L134 seem to be still alive.
But symptoms are still the same:
- High breathing frequency
- lying apathetically in the open, even in the light. Not hiding.
- lying on the ground, they are not up at the top. so probably not suffocating. O2 is fine. Nitrite 0.
- shooting around like torpedos. some of the bigger ones have scratches on their noses from swimming against stuff.
- spinning around.

Guppy and cherry shrimp still fine in the "old" tank. residents of the new tank still fine as well.
The water in the old tank is NOT smelling bad. Well it smells like a tank does. But not like something was rotting in there. No bubbles coming up from the sand.

here some more specs:

1. Water parameters
a) Temperature range: 28°C
b) pH 6.5-7
c) GH 2°
d) KH 2°
e)Ammonia: I don't know , Nitrate I don't know, Nitrite: 0,0mg/l
f) Water change frequency twice a week with 30-40%.


2. Tank set up
a) Size. 80x40x40 cm
b) Substrate. Sand
c) Filtration. Mattenfilter, air driven.
d) Furnishings.
e) Other tank mates. Guppy + cherry shrimp, both unaffected of illness.
f) How long has it been set-up? 8Months.
g) When was the last new fish added? no changes for some months.
h) Foods used and frequency? Sera viforma, frozen foods(black mosquito larvae, krill, brineshrimp) sometimes zucchini/cucumber/potatoe.

3. Symptoms / Problem description
- High breathing frequency
- lying apathetically in the open, even in the light. Not hiding.
- lying on the ground, they are not up at the top. so probably not suffocating. O2 is fine. Nitrite 0.
- shooting around like torpedos. some of the bigger ones have scratches on their noses from swimming against stuff.
- spinning around.
- dying

4. Action taken (if any)
2 Waterchanges 50%
moved them to another tank.

5. Medications used (if any)
none.

This is the first time plecos are dying on me. It is killing me! I love those tiny fellows.
Could this be an ammonia poisoning? Shouldn't they get better with waterchanges and a new tank without ammonia problems?

Any inputs? I don't want to see them suffer

[bekateen]

Hi Johannes,

Sorry to hear that. I had a similar die off (not of plecos, but a variety of fish) two years ago after a water change, and I considered the possibility of water poisoning too; I thought mine might be due to a temporary change in water quality from my municipal water supply. However, I've had other experiences since then, fortunately none with deaths, which make me consider sulfur poisoning as a culprit. You mentioned:

It all started with a water change round about 40% on thursday. While I was at it, I moved some of the sand

The water in the old tank is NOT smelling bad. Well it smells like a tank does. But not like something was rotting in there. No bubbles coming up from the sand.

Okay, but no bubbles at all? And no smell at all? How deep is your sand? I have found that even in 1-2 cm deep sand, I can get bubbles if I stir up the sand during a water change. This is especially true if any sand is disturbed underneath furniture, like caves, rocks, or driftwood; these structures create stagnant places where (I believe) anaerobic bacteria accumulate.

Whenever I see these bubbles, my solutions are three-fold: (1) Extreme water change (75%), (2) Add double-dose of SeaChem Prime (2ml/10gal, instead of the normal 1ml/10gal), and (3) very strong aeration. I don't know if the extra Prime does any good, but I use it anyway. I think the aeration is the most important action, followed by the extra water change.

One thing which I've found helps prevent this is the presence of corys in the tank, or other burrowing fish (like my banjos). They disrupt the sand so much that a thin layer of sand rarely seems to develop these anaerobic pockets.

I don't know if that's really the problem you had, but I hope the die-off is past.

Regards, Eric

[Jobro]

Just checked, your right, bubbles will come out if I move my finger through the sand right in front of the caves, right where I moved it on thursday. No bubbles elsewhere. Seems like I killed them by moving the sand. I was afraid this was the reason.

sulfur is supposed to smell of old eggs, right? can't smell that though. Maybe it's too little to smell. Still I'm positive something is wrong in the sand. though I have some snailes digging through it. that seems to be not enough to be save from sulfur.

I hoped moving them to another tank would help them. Maybe I should have moved them sooner
I don't want all of them to die. Any cures for sulfur poisoning? Any more hints what can be done to stop their suffering?

gotta google that seachem stuff...

Thanks Eric.

[bekateen]

I don't know if SeaChem Prime (http://www.seachem.com/Products/product ... Prime.html) is especially better than other chemicals. In the US, I've been told that this is a particularly good chlorine/chloramine/ammonia-removing mixture, good because it's concentrated and so you add very little of it to a tank (1ml/10gal, vs 5ml/10gal for products like Novaqua). But honestly, other than that, I don't know if the formulation is any different. I've also been told that people who sell fish and ship them by mail will add Prime to the water in the bag to help the fish handle the stress and ammonia buildup in the water during shipping.

Yes sulfur (in this case, hydrogen sulfide (H2S), although other members also mention sulfuric acid, H2SO4) is supposed to smell like rotten eggs. But if it's in small quantities and your tank already smells "fishy" (or swampy or however you might describe normal aquarium smells), I've found that I can't smell the sulfur. Of course, it is also possible that the gas isn't actually hydrogen sulfide, but something else (I know not what) which could harm the fish. Maybe a sudden influx of N2 gas or CO2 gas might also have negative effects (although likely less severe than hydrogen sulfide gas effects).

The issue of stirring up the gravel during water changes raises a couple of issues. For me, it's become standard practice, but I know some other people think it's a bad idea because it may disrupt the nitrogen cycle and the fish may be vulnerable to ammonia and nitrite poisoning for a time after the water change. But I have reservations about the universal validity of that statement. Now that you mention it, I think I should start a new thread in Tank Talk about other members' impressions on this practice, its risks and its benefits, and whether there are times/circumstances in which it's a good idea and times/circumstances in which it's a bad idea.

Cheers, Eric

[MarlonnekeW]

I'm very sorry to hear that you are having problems and some of your fish have died.

I'm still very inexperienced when it comes to pleco's, so I can't really help you, but could it be that loricariidae are a lot more sensitive to problems with the substrate than other fish?
I've experienced something similar with my Ancistrus claro. They were in a aquarium with baby Corydoras pygmaeus and Crystal red shrimp when I had some bubbles coming out of the sand. My claro's were clearly not ok, whereas the baby cory's and the shrimp were fine. Normally those are the ones that get effected very quickly and are the most vulnerable, but in this case they were not.

I'm keeping my fingers crossed that the rest of them will survive and get well soon!

[bekateen]

One more thought about the gas and its potential risks:

Caves and other such furniture may trap these gases when they are released in an aquarium. In one of the instances I was referring to in my tanks, I had a 1/2 coconut shell, buried partially in the sand as a cave for an

Apistogramma agassizii

. When the gravel was disturbed during a water change, bubbles rose in the tank. Most of the fish seemed unaffected. But inside the coconut shell the Apistogramma was laying on its side, breathing heavily. When I moved the coconut shell, a big bubble of gas was released from inside the shell (not from the sand). Apparently, the gas bubbles leaving the sand had become trapped in the coconut shell, poisoning the fish. I moved the fish to another tank and it eventually recovered. But I was very worried for a while there. As a result, I always make sure to disrupt the coconut shell and turn it upside down whenever I stir the gravel.

[TwoTankAmin]

It sure sounds like an ammonia spike. Spinning is often a symptom of ammonia poisoning. Stirring up one's substrate can cause an ammonia spike (due both to releasing decaying organics into the water and from burying the nitrifying bacteria living in the top .5 inches (or a tad less) of substrate. Because you had not tested for it, you would not have been able to see it. Then your water changes dropped the ammonia level before the expected nitrite spike had a chance to happen.

Is it possible your pH spiked in either direction? Normally, it takes a fair amount of total ammonia at your indicated pH to have enough be in the toxic NH3 form. A Total Ammonia reading of 4 ppm at pH 7.0 and 80F you would only have had only .0262 ppm of MH3. The line below which NH3 is safe for almost aquatic lifeforms is .02 ppm and the danger line for most fish is .05 ppm. At 6.5 rather then 7.0, you would have had .0083 ppm. When did you take the readings you indicated in your post? I doubt the ammonia got that high or higher based solely what you reported you did.

As for a fish killing contaminant in the water, they usually will affect all the fish in a tank. Ammonia, on the other hand, is more species specific in that different species have better resistance and other are more sensitive.

The only other place that might be the source of the problem would be your tap water. But then that would have shown some effects if you did water changes on other tanks in the same time range.

I agree that releasing hydrogen sulfide from one's substrate definitely gives off a strong odor like rotten eggs. Its hard to miss. Tilting pleco caves to be higher at the opening prevents the possibility of trapping gas in a cave as well as helping to keep eggs from rolling out .

[dw1305]

Hi all,
I'm sorry to hear of your problems, and it sounds like a dissolved oxygen issue, and these are often caused by increased levels ammonia (NH3).

As well as doing what the other posters have suggested I would add a power-head with venturi.

Have a look at <http://plecoplanet.com/?page_id=829> & <http://www.planetcatfish.com/forum/view ... 10&t=41716>, and Racoll's post in this thread <http://www.planetcatfish.com/forum/view ... ed#p284917>.

cheers Darrel

[bekateen]

Tilting pleco caves to be higher at the opening prevents the possibility of trapping gas in a cave as well as helping to keep eggs from rolling out .

Independent of everything else, this is great advice all on its own.

As well as doing what the other posters have suggested I would add a power-head with venturi.

A power-head with a venturi is a great idea; it's what I had in mind when I was describing very strong aeration. Currently I don't own one of thoese; I achieve this type of action on a day-to-day basis in my clown pleco tank by positioning an airstone underneath a recirculating pump (the Hydor Koralia nano in my 15gal); I do this just for the health of the clown plecos, independent of any potential build-up of toxic gases (their gravel is only about 0.5-1cm deep, so really nothing to worry about in that tank, I hope). But for my new tank, the one I'm setting up that's scheduled to receive the spotted orange seam plecos any day now, I plan to trade out the airstone/recirculating pump for an integrated pump with venture unit - not that the former is bad, but in this particular aquarium is located in a room of the house wherein I don't have the luxury of housing an air pump nearby, so a single integrated internal unit for high water circulation with direct aeration is very desirable.

[PseudaSmart]

Jobro, suddenly loosing fish is always stressful no matter how long you have kept fish. Complicating the issue is we have replaced "wait and see" with a "fix it now" mentally. It took me along time to learn to slow down.

Your first statement is the key but was never followed up. If it all started after the 40% WC then why was your source water never checked? If you do the two water changes a week as stated nothing 'hiding' in your tank would suddenly cause a problem unless you massively over feed. A tank running for 8 months has an established bio system and even stirring up the bottom would not make a difference.

Twotankamin is on the right path. Once the gills are damaged by ammonia past a level it is almost impossible for them to recover. There is no way to put them into an 'oxygen tent.' The bottom fish are affected first because the toxins tend to settle.

Until I started making my own water 100% of the time city water would give me similar issues when they over treated the system.

I'm starting to put together a list of truisms for keeping L-numbers or expensive fish in general. Here are three that apply.
1. The cost of a complete water test kit is less than one expensive fish.
2. Understand and test periodically the water going into the tanks - it changes, even well water.
3. Do not take water samples just from the top of a tank if there are problems.

Jim

[Jobro]

I am using almost only RO water. I have 5 tanks with plecos. All of them get the same water. Only one was affected. I doubt it was the water.
I changed the water of my L46 tank using the exact same water I used for the "sick" tank. I changed the water on both tanks almost simultaneously with the same water. Only one tank was affected, the one in which I moved the sand.

The fish also always stayed to the bottom of the tank. Plecos suffering from low aeriation will usually go to the top of the tank and stay very close to the surface. Not the case here. Adding more aeriation didn't fix it either. So more probably some sort of poisoning. Aeriation is so high, that almost no CO2 is dissolved in my tanks. That's why they stay around PH7 even when the Kh goes towards 0.

to be honest I didn't meassure PH at that time. Yes, would be definitely good to invest into ammonia readings. But the RO water is usually a little on the acid side. So there should be no huge spikes to more than PH 7. Still very much possible something like this happened here. Too bad I have no Ammonia readings and didn't meassure PH at the given time. I didn't know about the Ammonia to PH relation until you told me, so reading PH didn't make much sense to me. PH usually won't kill your plecos unless it goes quickly to sub PH5 or above PH 9, which was very unlikely in my tanks (I can't even get it below PH6.0 with KH 0 and using turf if I wanted, because so little CO2 is dissolved)
And even the tap water only has something like PH 7.6-8.0. PH was just so far out of the question for me, I didn't consider meassuring. Will do if I ever have trouble like this again.

Found another dead L333 today. Makes 5 out of 6.
L260 are not looking good either. A lot of injuries and fins all damaged by the continous mad swimming through the tank. they act like mad
L134 are a bit better. I hope at least those will make it.

Seeing them die and being unable to do anything but waterchanges - without any effects - really makes me mad as well. I can't watch them any longer. It really hits you deep, seeing those cute little plecos suffer like this. Thinking about giving away all of my plecos when this is over. This is just too much right now. I always tried hard to make them feel well and cared a lot. Never expected something could go wrong like this. Don't know if I could cope with something like this happening again.

Thanks for all your support and condolence. This helps quite a lot. Thanks.
Johannes.

[MarlonnekeW]

It's probably a long shot, but just in case: Do you own a dog or a cat and did you give them 'spot-on' drops to prevent flees and ticks?
It's not well known, but these products can be very harmful to aquatic life. The biggest problem is that, when your skin comes in contact with it, the substance is absorbed by your skin, so washing your hands doesn't help. If you then put your hands in the aquarium, you can poison it. I'm 100% sure that this is very harmful to shrimps and I wouldn't be surprised if it will effect vulnerable fish as well.

The chance is of course very slim that this is the problem, but you never know...

[PseudaSmart]

Johannes,
I say this with kindness from having the same experience about 6 months ago, you are making too many conclusions with flawed assumptions. When you run water that soft how you measure and what you use to measure is important. I have found that dip strips, hand held meters, and titration kits will give day defferent results.

What do you add to your RO water before doing the water changes? My issues stopped when I switched from a homemade buffer recipe to Netural Regulator by Seachem. I continue to use RO Right for my GH. (Yes I am aware of all the discussion about RO Right but my results!)

Like you my tanks ran fine for a longtime. First my L333s started to die followed by abns (and those are indestructible). My best guess is that an essential nutrient was gradually depleted. Cactus plecos have large spawns and I am back to almost zero daily deaths once again.

Jim

[Jobro]

No, I don't have other pets around and I didn't get in contact with any lately(as far as I remember). I'm pretty sure pharmacies like those would hurt plecos a lot though.

I measure with Sera titration kits. No idea how accurate they are. But it's not like I need to know if my PH is 7.0 or 6.8. Neither if nitrite is 0.3 or 0.5, I just need to know it's non existent or existent, only one of those is desired.

I only add some very little tap water to my RO water to get it to ~100ms/cm², which I measure with a handheld device. Water quality is not an issue in germany. Tap-water is less polluted than most soda you could buy bottled up in a shop. It is strongly regulated and controlled. It's just very hard, that's why I need the RO.
As shrimps tend to be very vulnerable to copper and other "heavy metals" (Is this really the right translation? sounds like a music genre..) in the water, I'm pretty sure this can't be a copper poisoning. And copper would be the only thing that could be in my water, except for maybe chloride, but I always let the water breath for a day before I pour it into a tank so it shouldn't be chloride either. Cherry shrimps and snails are supposed to die by chloride as well, but those are still fine.

You really think all plecos in the tank would start with similar symptoms simultaneously due to a essential nutrient lacking in the water? Even though the fish were placed into that water at 4 different times. (first were 3 small L260s, later 2 "a little bigger" L260s, then 6 L333 and then 6 L134 with some weeks in between each). Lack of nutrients wouldn't pop up on all at the same time now I guess, would it?
I had this trouble of "too soft water" with german blue ram youngsters before, too. Out of 30 youngsters there were only a few that got "hole in the head" disease, most were not affected at all. Adding some Sera mineral salt, going up to ~200ms/cm² (from below 100ms/cm²) made all the holes disappear. But the lack of nutrients didn't show up on all individuals at the same time and those fish were all from the same offspring and hence in the same water for all their life and had similar genetics. Yet, lack of nutrients was, in this case, not visible on all at the same time and neither to the same degree.
I just can't see all of the plecos starting to suffer at the same time by a nutrient lack. And only in one tank, when I have L46 youngsters in the same water for an even longer time without symptoms. I know l46 are not very demanding, but L333 are neither. This points much rather to a tank related problem than a water related problem.

please don't get me wrong. it's not like I'm trying to devote truth here. I am pretty certain it was my fault those poor fellows are dying and I am not going to deny it. The ammonia or sulfur theory just seems to be way more plausible than a nutrient lack to me.

Another L260 dead

As they are still breathing so fast after being in a different, well aeriated tank for more than 3 days, I assume their gills are really damaged and are probably not going to recover.

The number of tiny glas-worms is decreasing very fast in the "sick" tank by now. Looks like the pike is over.

[PseudaSmart]

Johannes,
I never considered that you trying to do anything but find answers. Sometimes we move to fast down a path without enough information. Your last few posts have provided valuable information.
RO water is used for water changes with some tap water added back.
The KH sometimes goes to zero.
A tank with L46s used the same water w/o issues(very important!)
While typing the last post I was considering several different possibilities and they got blended together. Nutrients was a poor word to use.

The first potential cause was ammonia burn on gills caused by stirring up gravel and low water buffering.
The second thought, which I am still trying to describe in simple terms is an osmotic pressure or electrolyte imbalance. Cells either absorb water or emit water trying to balance with their environment. If they absorb too much water they explode. The gills and the blood cells are the most sensitive. That is why almost all fish cannot live in RO water and why it is easier to move a fish from soft to hard water.
The third thought, based on the new info, is all of the stirred up sand could have damaged their gills. Or they all panicked and stacked up in the corners or a cave and partially suffocated. You did mention scrapes and some of the adults. Once while doing a water change I watched in horror as over a dozen L600 juveniles spooked and jammed into a small cave I had been meaning to take out. In only minutes all but four were dead.

I hope these suggestions help you find the answer. Every detail is important.

FYI the Ph scale is not linear but log. Ph of 7 is 10x more acidic then 8 and 100x more than 9. There is always dissolved CO2 in water. In fact heavy aeration allows the maximum amount to be absorbed as dictated by the Ph and the buffering of the water. Any gas bubble that forms in the water means that locally maximum saturation has been reached and it is being forced out of solution. Very little is absorbed back into the water as the bubble raises to the surface.
Jim

[Jobro]

Hey Jim,

The KH sometimes goes to zero.

Well in those pleco tanks It shouldn't be that low, as I always add some tap. I was referring to my apistogramma tanks. Those are RO-Water only and even those wont go below PH6.0. Using air-lift pumps makes it really hard to get lower than PH 6. I would love to have Ph5 for my Apistogramma though.

The first potential cause was ammonia burn on gills caused by stirring up gravel and low water buffering.

This is still the best assumption for me. The fish are still suffering badly and they seem to have trouble breathing. After almost a whole week in a different tank now!

he second thought, which I am still trying to describe in simple terms is an osmotic pressure or electrolyte imbalance. Cells either absorb water or emit water trying to balance with their environment. If they absorb too much water they explode. The gills and the blood cells are the most sensitive. That is why almost all fish cannot live in RO water and why it is easier to move a fish from soft to hard water.

I do know about osmotic pressure. You're right, this can be quite some problem with fish. Didn't notice it on plecos yet. Anything documented about plecos and "too soft water"? I'd assume some are coming from very very soft water? You suggest going with harder water would be better for the plecos? Well, I could save a lot of RO water...
Still I can't imagine all 17 plecos having exploded gills by osmotic pressure at once. How would the chances be for something like this to happen to all at the same time?

The third thought, based on the new info, is all of the stirred up sand could have damaged their gills. Or they all panicked and stacked up in the corners or a cave and partially suffocated. You did mention scrapes and some of the adults. Once while doing a water change I watched in horror as over a dozen L600 juveniles spooked and jammed into a small cave I had been meaning to take out. In only minutes all but four were dead.

Again, how would this happen to 17 out of 17 plecos in a tank? Also those plecos love to dig in this sand. They would have way more and often problems. I have the same sand in all my tanks. The sand is pretty heavy as well, it's not like it's going to float through the water and need 1 hour to settle again or something, it will sink right away. The water didn't get like a sandstorm or anything, I just moved the sand along the ground like a bulldozer would. Probably burying something while doing this.
Also there are more caves than plecos. Each has his own. Of course each of them would start fanning or try to hide deeper in the cave. But plecos at the size of 4cm+ wouldn't die by some stress in their caves. It only took me like 10 seconds to move that sand. Not like they were panicking for hours. Also don't forget I removed all 17 by my own hand. They did not have any visual injuries or outter signs of disease at that time. Everyone should examine their plecos properly when he has a problem like this. And so did I. I couldn't find anything on them. No red pectoral fins or something. The injuries only popped up after rampaging for 2 days in the new tank. Mostly rubbed sore noses and torn fins.

In fact heavy aeration allows the maximum amount to be absorbed as dictated by the Ph and the buffering of the water

Not sure if I am running into a language barrier here, but I understand this as "More aeration will put more CO2 into the water"?
Everywhere I read that CO2 will be dissolved out of the water with strong aeriation and much water movement on the surface. Your statement would point to the opposite? In my experience aeration will raise PH by driving out the CO2.

Sadly I have to announce two more casualties, 1 L260 and 1 L134 as well. Was hoping the L134 would make it... this points otherweise

[dw1305]

Hi all,

Not sure if I am running into a language barrier here, but I understand this as "More aeration will put more CO2 into the water"?
Everywhere I read that CO2 will be dissolved out of the water with strong aeriation and much water movement on the surface. Your statement would point to the opposite? In my experience aeration will raise PH by driving out the CO2.

Curiously both opinions can be correct. It depends a lot on tank architecture, the bio-load etc.

Have a look at "Aeration and dissolved oxygen in the aquarium" (http://plecoplanet.com/?page_id=829), this isn't an entirely objective opinion, but I think it covers this whole area fairly well.

The important bit is that if you have a large gas exchange surface then the levels of dissolved gases will remain closer to equilibrium with atmospheric values. If running an air stone has a dramatic effect on pH, then that strongly suggests to me that you don't normally have a large enough gas exchange surface for your bioload.

Technical Bit
Oxygen is a base, a "proton (H+ ion) acceptor" (so OH- , is really O-H), and raises pH. CO2 is an acid, a "proton donor". In this case it is the very small proportion of CO2 (less than 1%), that goes into solution as H2CO3 that lowers pH.

Unless we add pressurised CO2, the pH of our water will usually depend upon the reservoir of carbonate buffering (dKH), and the CO2 <> HCO3- equilibrium (http://lawr.ucdavis.edu/classes/ssc102/Section5.pdf).

There is a proviso to this, and that is that pH is a ratio and as we approach pure H2O (0dKH) pH is a less relevant measure, where small changes in water chemistry cause large changes in pH.

The atmosphere is ~21% oxygen (O2), but oxygen had a relatively low solubility in water (the actual figure is dependent upon temperature, salinity and atmospheric pressure for all dissolved gases - Henry's law (<https://en.wikipedia.org/wiki/Henry's_law>) etc). Carbon dioxide (CO2) is only about ~400ppm of the atmosphere, but is more soluble in water.

At standard ambient temperature and pressure (25oC and 1013 mb) pure H2O is saturated with 8.2mg/l oxygen, and about 0.5 ppm CO2.

cheers Darrel

[PseudaSmart]

Johannes,
I hope you are closer to finding out what happened. It sounds like there is a new lesson to be learned for many of us. My mistakes are usually combinations not just one thing.

Darrel,
Thanks for adding detail to the thread. Information is only useful when placed in the proper context( which I did not do). My CO2 example is from when I adjust my pure RO water. When it first fills the tub the ph is mid 7's, same as from the well. Add an air stone it drops to almost 6 because there is no buffer in the water. Then I adjust as needed.

Pleco fry do grow faster and better in 'harder' water but not 'hard' water - this is another thread entirely.

Jim

[dw1305]

Hi all,

......My CO2 example is from when I adjust my pure RO water. When it first fills the tub the ph is mid 7's, same as from the well. Add an air stone it drops to almost 6 because there is no buffer in the water.

That is strange, if the water is 100% RO (so actually water, H2O, rather than the dilute solutions we normally call "water", where salts are dissolved with H2O as the solvent) the pH should equilibrate, at atmospheric gas levels, to ~pH5.6.

The reason that pure water is acidic is the dissolved atmospheric CO2. So even though we start with 10-7 H+ ions and 10-7 OH- ions, we get:

CO2 + H2O > H2CO3 and then HCO3 > H+ & HCO3-

The excess of H+ ions (over OH- ions) lowers the pH (pH is the ratio of H+:OH- ions expressed as the negative log10 of the H+ ion activity).

Pleco fry do grow faster and better in 'harder' water but not 'hard' water - this is another thread entirely

Yes I think they do as well, unless there was a very good reason not too I'd buffer the water to about 4dKH.

One advantage is that it allows you to put MTS with the eggs and fry, (and Red ramshorn snails with the fry) as "janitors". I got the idea from Ingo Seidel (<"http://www.planetcatfish.com/forum/view ... hp?t=36665">).

I tend to ignore pH all together in very soft water, and just use conductivity as a measure of the suitability of the water.

cheers Darrel