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Hi folks,
I'm new to these boards, but have been impressed with the breadth of knowledge and experience within the forums. My wife has had Corys for awhile, but I'm trying to learn to take care of the tank and these fish appropriately.

Anyway, the pH in our tank has been creeping on the low side for the last few weeks or so although it's unclear why. Using the API kit, it has been wavering between 6.4 and 6.0 and now is pretty much at 6.0 unless I do water changes (which I did about 2-3 times a week, maybe 15% at a time). Since we live in Sacramento, CA, the temperatures have also been rising due to our summertime with room temperatures getting into the low 80's although the tank temperature runs probably 78-82 depending on the time of day. Since we are not at home most of the time, we at least leave the ceiling fan on, but have not resorted to turning on the A/C with temperature control limits yet.

We originally have had a Cory Metae (living for almost 10 years wow), then recently added two Sturbai and a panda about 1-2 weeks ago since the Metae's offspring sadly passed away (maybe only lived about 5-6 years and was never as robust or big). We were worried that our sole Metae might've become lonely and were quite pleased that he/she perked up after adding some other Corys. Our four fish seemed fairly active the first week or so and were even wandering around and snooting during the daytime, however seem to have taken towards hiding out underneath the heater or other overhanging areas unless food is around. Odd since the Sturbai were actually very active at some point.

My conditions:
1. Water parameters
a) 78-82F
b) pH ~ 6.0
c) hardness 75
d) alkalinity 120
e) NH3 0.2, Nitrite 0, Nitrate 20
f) water change freq- 2-3 x a week for last week

Tank setup:
a) 15 gallon
b) Substrate- sand mostly, some small pebbles
c) filtration - two Aquaclear mini 20 filters
d) one piece of driftwood. some aquatic plants that I'm not sure of, sorry. maybe java ferns.
e) tankmates - as above - one cory metae, two sturbai, one panda.
f) tank has been set up for at least two years.. up until two weeks ago, it pretty much only had 1-2 cory metaes living in it.

Symptoms: lethargy

Actions: water changes as mentioned above. no medications used.

- so my questions are:

1. Can I use a product such as the API Proper pH 7.0 buffer to help adjust and stabilize my pH? Will this affect either the Corys or the aquatic plants?

2. How much does pH and/or heat play a factor in stress?

3. Do you have any good tips on trying to cool down my tank during the summer time? I am already considering shortening the timer on the light (currently from about 10:30am to 9:30pm) for less hours of light since the room the tank's in has a fair amount of light despite having all the window shades down. The room is also my living room and thus hard to cool down quickly although I do have a ceiling fan right above the tank which I am running in addition to occasional A/C.

Any advice would be greatly appreciated. I've added a link to a youtube clip of the fish to show how active they were prior to this past week. http://www.youtube.com/watch?v=QwuX0HTGi0s. I love Corys and would hope to really learn to take care of them well. (Wish I had gained experience on other fish or a different tank prior to these guys)

Thanks!

In general, I'd say your numbers seem good for Corys. Lower than pH 7 is fine for corys - as long as it's not TOO low - for many fish, pH 4.0 is survivable (not saying recommended).

I'd be slightly more worried about the ammonia (NH3) levels being non-zero. That, to me, indicates there's something not right with your beneficial bacteria in the filter (or the test is wrong).

If you do feel you should up the pH a little bit, I'd suggest a KH (KH == alkalinity) buffer - baking soda from the supermarket works great for this. You only need TINY amounts. I take it your "alkalinity" measure is AFTER water change - I'd expect 120 ppm KH would be sufficient to keep your pH around 6.5. And you should be happy that your tap-water is quite soft - it's MUCH harder to fix water that is high in minerals (hardness GH/ alkalinity KH).

As to temperature, I would think that around 80'F is fine for C. metae & C. sterbai (I have been keeping both of these at those sort of temperatures), but C. panda would prefer a lower temperature - below 75'F would be ideal.

I would also suggest that it's best to keep corys in a group of 5-6 (at least) of the same species, rather than "pick'n'mix" style of one or two of each kind.

--
Mats

MatsP wrote:In general, I'd say your numbers seem good for Corys. Lower than pH 7 is fine for corys - as long as it's not TOO low - for many fish, pH 4.0 is survivable (not saying recommended).

I'd be slightly more worried about the ammonia (NH3) levels being non-zero. That, to me, indicates there's something not right with your beneficial bacteria in the filter (or the test is wrong).

If you do feel you should up the pH a little bit, I'd suggest a KH (KH == alkalinity) buffer - baking soda from the supermarket works great for this. You only need TINY amounts. I take it your "alkalinity" measure is AFTER water change - I'd expect 120 ppm KH would be sufficient to keep your pH around 6.5. And you should be happy that your tap-water is quite soft - it's MUCH harder to fix water that is high in minerals (hardness GH/ alkalinity KH).

As to temperature, I would think that around 80'F is fine for C. metae & C. sterbai (I have been keeping both of these at those sort of temperatures), but C. panda would prefer a lower temperature - below 75'F would be ideal.

I would also suggest that it's best to keep corys in a group of 5-6 (at least) of the same species, rather than "pick'n'mix" style of one or two of each kind.

--
Mats

Hi Mats,
Thank you for the responses. I wanted to reply with more information. I forgot to add earlier that our tap water is pH 7.6.

Since we are a bit hesitant to make any big changes, we sought out other opinions as well. Aside from the temperature issue, others showed some concern about the Nitrate level as well as the acidic pH to a lesser extent. Some felt we were doing water changes too frequently (2-3x a week) and/or said that b/c we had been using the vacuum to clean the substrate, we were sucking up some of the beneficial bacteria which might have been contributing to pH issues. Other recommendations included addition of pH buffer your suggestion for the baking soda, use of beneficial bacteria with a large water change, or even using KH booster and discus buffer as well as bacteria.

So anyway, we ended up going with a more conservative approach to try and improve the pH a bit.

- Do smaller and less frequent water changes of perhaps 15-20% about 1-2 x a week and not taking water off the bottom of the tank
- Start adding Nutrafin Cycle biological aquarium supplementation based on directed doses of about 7.5ml each time(although LFS guy recommended dumping in a lot more i.e. 25ml with an significant water change of about 50%).
- Added a one time dose of API Proper pH 7.0

My numbers right before we did all this:
pH 5.5 (or somewhere near this b/c our test strips cannot go any lower)
Alkalinity 120
GH 75
Nitrite 0
Nitrate 20-40
NH3 n/a

After about a week, these are the resultant numbers (a few days after most recent water change:
pH 5.5
Alkalinity 0
GH 0
Nitrite 0
Nitrate 20-40
NH3 0

Fish look same and not much better. We are making sure not to feed them too much to avoid extra waste production.

My thoughts/questions at this point:
1. Is it really poor form to use the water vacuum on the substrate as this may remove beneficial bacteria?
2. Is the addition of beneficial bacteria fairly harmless? Is there any potential upside to adding more than as directed on the product? My hope is that the additional bacteria may help decrease the amt of nitrates.

3. Our KH and GH appear to have dropped. Does this make sense based on our actions of adding more beneficial bacteria and adding a single dose of pH buffer?

4. Should I be concerned about trying to figure out just how low the pH really is? (our API pH kit and Mardel 5-in-1 test strips can't measure below 6.0 or 5.5.)

5. We've only tried the Proper pH 7.0 product once.. so far it hasn't killed our few live aquatic plants. We were hesitant about using the baking soda b/c of reading some comments about baking soda's effect not lasting and potentially causing some pH swings. One other suggestion I've read about is the addition of things such as crushed coral, sea shells, limestone rock, etc to raise the GH/KH and its buffering capabilities.

Thoughts?

1. Is it really poor form to use the water vacuum on the substrate as this may remove beneficial bacteria?

1. Gravel vacuum is not going to (much) affect your beneficial bacteria. It WILL affect the pH in the sense that the detritus will acidify your water. So if you want to fix your pH problem, cleaning up the substrate is a GOOD idea.

2. Is the addition of beneficial bacteria fairly harmless? Is there any potential upside to adding more than as directed on the product? My hope is that the additional bacteria may help decrease the amt of nitrates.

I think you do have sufficient beneficial bacteria if your NH3/NO2 (ammonia/nitrite) levels are zero - which is what you report now. Adding MORE beneficial bacteria will have very little effect.

3. Our KH and GH appear to have dropped. Does this make sense based on our actions of adding more beneficial bacteria and adding a single dose of pH buffer?

When the beneficial bacteria will use up KH when producing nitrate from ammonia.

4. Should I be concerned about trying to figure out just how low the pH really is? (our API pH kit and Mardel 5-in-1 test strips can't measure below 6.0 or 5.5.)

No, you should be concerned than your KH/Alkalinity is zero - that's not good, and it allows the pH to go low - low pH in and of itself isn't what is bad - it's the fact that the KH is low that leads to low pH, and measuring KH is a better suggestion than trying to figure out HOW low your pH is - the FIX is to raise the KH - that will bring the pH up as well. It's a bit like knowing you have a puncture, and then trying to figure out exactly what your tyre pressure is before putting a patch in to cover the hole made by the nail.

5. We've only tried the Proper pH 7.0 product once.. so far it hasn't killed our few live aquatic plants. We were hesitant about using the baking soda b/c of reading some comments about baking soda's effect not lasting and potentially causing some pH swings. One other suggestion I've read about is the addition of things such as crushed coral, sea shells, limestone rock, etc to raise the GH/KH and its buffering capabilities.

Yes, if you use bicarbonate, you will need to CHECK the KH value regularly, and top up. But this applies to adding sea-shells, limestone rock etc too - yes, those are slightly less "immediate", so it will take a bit longer to bring the KH up/down, but it's also harder to control the exact values. Since it seems your tap-water contains a decent amount of KH, I'm still inclined to try to go for a larger water change principle. See comment below about "Proper pH" type of products.


A few further comments:
* I'm not sure why you feel that large water changes would be such a problem... I do weekly 50% water changes on all my tanks, and have done for a few weeks. Never had a problem with it, and I don't know of anyone who does REGULAR large water changes that have reported that it's a problem. I do know (of) a lot of pages on the internet that say "don't do large water changes", but I've so far not found anyone who actually has anything other than hearsay ("The shop told me when I bought my tank ..." or "My friend says ...") that small water changes are better. [Not including "Old Tank Syndrom".]

I had a rack (before divorce... ) in my fishroom that was fed by the waste-water of my RO system. There were four 100 liter (approx 25g) tanks in the rack, and the RO system was a 50gpd system - in actual fact it produced about 30gpd, but RO systems produce about 4x the volume of waste-water, so about 120g per day of waste. This means that the 100g of water in the 4 tanks would be replaced more than once every day! I had absolutely no problems in those tanks that I could even remotely blame on water changes. I did have a male ancistrus kill another male, and I lost a Dwarf Giraffe Cat due to a crushing accident with a piece of wood. But can't blame either on the water in my book... ;)

* I'm suspicious at "pH correcting additives". I personally do not beleive they do what the user of them intends. Yes, of course, it DOES alter the pH [assuming the product isn't a complete fake, and I'm not awarey of any indiciation of this being the case - and it would be pretty easy to prove with a pH meter or similar] - but why is low pH so bad? Well, we don't really understand to 100% why the beneficial bacteria dislikes low pH, but one theory is that it's lack of carbonate (CO3--) ions (so KH, essentially) [1]. Adding a KH buffer is fine - that's what you find in natural pH balanced water.

The "lowering pH" products are even worse, since low pH is generally low conductivity, and this type of product CAN NOT POSSIBLY lower the conductivity of the water, so while the pH may be affected in the right direction, the OTHER component that you want to change (conductivity) will move in the WRONG direction.

So, in conclusion:
Make larger water changes with dechlorinated tap-water. Don't use "pH adjusting additives". Add KH buffer if needed (whatever form you like, limestone, seashells or baking soda) [note that there is no KH buffer that has a permanent/lasting effect - but if you add say a piece of limestone rock, it will dissolve pretty slowly in your water, and as long as there is a decent amount of rock still left, it will continue to do so as long as the pH is low enough to dissolve the rock (below 8.2 or so). Of course, if you add a HUGE rock, it will get to pH 8.2 in short order.

[1] A post on another forum said that "when using limestone granules as a bacterial substrate, the low pH doesn't seem to affect the beneficial bacteria". Since limestone in an acidic is a source of carbonate ions, what the researchers should have done was to add some OTHER carbonate source to prove that carbonate, rather than the limestone granules as such, was/was not the source of "working bacteria".

--
Mats

When I lived in Seattle and had large Planted tanks, I would do very large water changes over 50% on a bi-weekly basis. It never affected the fish. I always noticed the water had a stronger chlorinated smell in the summer as if the municipality added more to prevent algae. I did use a carbon filter to filter the water though.

Hey Melancholy, don't be sad

An aquaclear mini20 filter is for a 10gallon tank (I googled) and you have 2. For greater stability you might consider replacing your mini filters and invest in a much bigger filter that has more media capacity. I would suggest a filter that can handle at least double, even triple... your tank volume. A filter with an outlet at the surface to create a strong current around the tank... your corys will appreciate this. They will find the calmer spots where they can sit when they want to. Strong aeration will help your corys during warmer months.

I would only try to change 50% of the water every 4 days and not try to alter the water chemistry.

The ammonia spike does imply that your biological filter experienced a setback for some reason but if you continue with these water changes the filter will return to normal.
Trying to achieve a hardness and pH that is different from your tap water usually causes more problems for fish than it solves unless you have naturally soft water and desire a more acidic pH which will occur without having to do anything.
I think your Corydoras should be considered such a fish; one which will do well in soft acid water.

The changes in behavior are probably due to the fact that the Corydoras finally figured out that they were different species so they lost that initial sense of security they derived from being with similar species. As has been pointed out, it is best to keep 5 or 6 of one species of Corydoras.