water levels

[kvnbyl]

I've noticed something that I find curious. Quite a few of the tank pictures show tanks maybe 2/3 full, sometimes even a little less. I've always wondered why. I understand that for breeding purposes the water level needs to be brought down, I've bred corydoras cats and have done the "simulate the monsoon season thing" but these seem to be everyday tanks. Why would you buy a 90 gallon tank and only put 60 or even 75 gallon gallons of water in it? As it is, a 90 gallon thank would have to be filled right to the top to hold 90 gallons so we are already down 5 or 10% from the tank specs. I'm not saying it's wrong, everyone has a right to do their own thing. I keep my tanks filled up past the frame, as i want to see something like a picture, water and then frame. I use large canister filters because they really stir up the surface if pointed right and supplemental aeration mostly 'cause I like it so maybe that's it. Is it to facilitate the Co2 / O2 exchange? Is it something i am doing wrong? Please don't jump on me, I'm just curious
Thanks!
kvnbyl

[Bas Pels]

I can't tel you why, assuming your observation is correct.

My tanks normally have a few cm empty, in order to keep water from flowing out.

BUT when you want to keep X fishes in a tank, the amount of liters is far less important than the surface. And this is the same, regardless the depth of the water

[dw1305]

Hi all,

I've noticed something that I find curious. Quite a few of the tank pictures show tanks maybe 2/3 full, sometimes even a little less. ........ Is it to facilitate the Co2 / O2 exchange? Is it something i am doing wrong?

BUT when you want to keep X fishes in a tank, the amount of liters is far less important than the surface. And this is the same, regardless the depth of the water

@Bas Pels is right, surface area (the gas exchange surface) is the important factor, not so much the volume of water.

I use canister filters, but I have some reservations about them, mainly that a fixed amount of oxygen enters the filter body and it can't be replenished in the filter, until fresh oxygenated water flows in. Whatever any-one else tells you, you can never have too much oxygen in your filter.

Personally I don't fill most of my tanks all the way to the top. When we had planted over-tank trickle filters (looking at phytoremediation) it was to give room for the plants and filter to sit in the tank, but still be under the lights. It also allowed the returning water (I used guttering to sit the plants, and hydroleca, in) to flow into the tank via a "waterfall" ensuring that the returning water was fully oxygenated. The "water" in the system had a high BOD, so oxygenation was very important

Initially when I had canister filters (the tanks are now at home, or in the teaching lab.) I had the return falling under gravity into the tank from a nozzle or spray bar, but it was much too noisy.

I went to using a venturi on the out-let, and that means that the water level needs to be a little bit lower than the rim to avoid water loss, it also allows room for floating and emergent plants.

cheers Darrel

[kvnbyl]

yeah but with so many easy ways of facilitating the gas exchange does it really matter where the surface is? i'm not talking a quarter of an inch, half maybe. It's so easy to add an airstone, or a surface pump and get that surface moving
I have a 75 gallon and a 110, same tank length and height and and then there is a rather large difference in height. Surface - area wise, the same tank, both have the same filtration relatively, the 75 has two 2215s and the 110 has two 2217s. I have never noticed any difference in behavior in the sense of gasping for air, hanging under the water surface, that kind of thing. At one point I had air stones in the tank but the water on the glass top right over the airstone was ruining the glass. so i cut back little by little until the air stone was off and saw no difference. Also, At his point there a lot more fish in the 110 because of the need to replace and old tank and i still don't see any differene. i tend to think that even with a small amount of water movement at the surface and some circulation top to bottom things remain fairly stable, . i'm not talking about a completely stagnant tank, i'm talking about reasonable filtration. nor am i talking about a very heavily stocked tank. they have tanks at the dealer i go to and even though i can't bear to look at the hundreds of feeder goldfish, I do. this is a grossly overstocked tank and even with a single filter hundreds of fish survive (survival being a relative term in these tanks)
Also, i switch my filters off during nightly feeding and have forgotten to turn them on and there were no deaths and to my surprise the filter showed no ill effects. i had expected sulphur dioxide but the only smell was a little of the fish room smell, the kind of algae and water thing. the water was clear so there had been no bacterial die off. Water seems to hold O2 for a very long time. note: I clean my filters often, with tank water as there is very little reason not to and getting large amounts of junk out of the tank cannot be a bad thing (A gentle clean, that is, more like a rinse) I see no reason to leave all that muck essentially still in the water column.
I have had filters go two full days and still be okay but like a said I keep my filters pretty clean if it is done right there is no reason not to.
when i buy fish from Florida i continue to be amazed that they can ship even relatively large fish and they survive in even maybe 8 or 10 ounces of water, i know that they take precautions but even so these fish have very little o2 and seem to do well (well lets go with "okay" it's maybe is a better term for some of the near disasters I have seen)
I think think that even with just an airstone or a sponge filter the playing field is very much leveled off. this is over four decades of fish keeping and i am no expert nor do i have an O2 meter unfortunately but observation would seem to indicate that there just is no need to fill a tank two thirds full ( not to even mention the price of tank "real estate")
Additionally, why not give the fish more room to swim? why should they only have 60 gallons of room when there is 90 available? get an airstone or a circulation pump and fill it up! leave a little space in that tightly fitting cover.
I know that this is an argument I am never going to win but i believe that with proper supplementary filtration / circulation
you can fill the tank up. The old rules said no, but they also said 1 inch of fish per gallon of waster? and we know that is a very relative statement. Filtration and water movement just blow that right out of the water:) (we are talking large tanks here, a 10 or a 20 long is not really relevant here) Not to mention that with xtra swimming space there will be less hostility between fish that can be agressive. (NOT catfish or course, they always get along, being that they are very, very nearly perfect life form....... )

[dw1305]

Hi all,

yeah but with so many easy ways of facilitating the gas exchange does it really matter where the surface is? i'm not talking a quarter of an inch, half maybe. It's so easy to add an airstone, or a surface pump and get that surface moving..........I have never noticed any difference in behavior in the sense of gasping for air, hanging under the water surface, that kind of thing. At one point I had air stones in the tank but the water on the glass top right over the airstone was ruining the glass.

I don't think there is a wrong or a right answer.

It is whatever works for you. I'm not a particularly good fish-keeper, and I have long periods where I can't regularly maintain the tanks, so I like set-ups that are pretty stable and resilient. I'm an Eheim Classic fan as well for that reason, I don't want bells and whistles, I want something that works.

Also I'm probably overly cautious, but fish can be suffering from low oxygen levels (and or high CO2 levels) long before they display obvious signs of distress.

The problem with oxygenation (and all dissolved gases) is that it is pretty difficult to measure, you can measure it accurately with a dissolved oxygen meter, but they aren't every day bits of kit. You can also use the 5 day BOD test, but again it isn't really feasible outside of a lab.

There are ways of estimating oxygen demand and increasing water quality and oxygen availability, if people are interested I wrote this article <"Plecoplanet: Aeration and dissolved oxygen in the aquarium(http://plecoplanet.com/?page_id=829)"> a few years ago specifically for keepers of rheophilic plecs, but it is relevant to all fish keeping.

If I was to use an air-pump (and I would if I had more tanks) I would definitely go down the jet-lifter (that "Swiss Tropicals" sell) route. You really need to use an uplift tube with an air stone for it to be effective.

cheers Darrel

[kvnbyl]

PINPOINT® II Oxygen Monitor, there is always this for about 250.00, 217 euros but honestly it's easier just to add an airstone. i have used swiss tropicals products for years and they are good, aimed more toward filtration but will help out enormously with aeration too.

[Bas Pels]

As I wrote, where the surface is, does not matter for gas exchange, untes the glass touches the cover That however is a bit too absurd to take into account.

A large body of water is more stable - both in temperature and in chemistry, and therefore, in most cases one would want to have the amount of water as big as possible.

But, when medicating a tank, it could save costs to lower the amount of water. Further some fishes, among which swordtails, prefer to have a cool night and a warm day, which is very hard to get. Just to be fully complete, platyfish don't.

[kvnbyl]

then you agree that it makes no sense (except in some really specific instances) to keep the water level low:

if it does not matter where the water level is as long as there is a reasonable amount of space between the cover glass and the water surface - fill it up, more swimming room

if a large body of water is more stable then a 90 gallon should have 90 gallons in it,. not 60, fill it up

it could save medicine costs to treat 60 gallons rather than 90 but for the once a year you do have to treat (less if you quarantine) why not fill it up, makes little sense to keep the water level low just in case you might have to treat the tank

if some fish prefer to the have some temperature differential than that makes the case for a tall tank again since a higher water column is going to have the most differential

i think the only real case to be made is that less water needs less filtration but that is kind an odd attitude, just buy a smaller tank?

[racoll]

I keep my water levels low because it allows the plants to emerge, and also stops the fish getting out. Not nice finding them all crispy on the floor in the morning.

[dw1305]

Hi all,

if it does not matter where the water level is as long as there is a reasonable amount of space between the cover glass and the water surface - fill it up, more swimming room. If a large body of water is more stable then a 90 gallon should have 90 gallons in it,. not 60, fill it up

Yes, I don't think any-one is arguing that you should leave the tank 2/3 full, unless there is a good reason. As you say a large volume of water is more stable and dilutes the ammonia produced by the fish more effectively. If I don't have an in tank trickle filter I'm only talking about a couple of inches of air-gap.

......i think the only real case to be made is that less water needs less filtration but that is kind an odd attitude, just buy a smaller tank?

I'm not suggesting have less water because it needs less filtration.

It is really back to what you mean by filtration, if you mean a larger filter is more efficient at pulling debris out of the water column, then I don't want my filter to act as a syphon, I want all my mechanical filtration outside of the filter body.

A larger filter will supply more flow (will move a larger volume of water), but again I'm mainly interested in water movement in terms of increasing the gas exchange surface area and providing some flow for riverine (rheophilic) fish.

Biological filtration is almost always limited limited by oxygen availability, it isn't limited by sites where nitrification can occur, (unless you go down the "bare tank, no substrate" route and I'm never going to) so for me a larger capacity filter doesn't necessarily mean more filtration capacity.

I keep my water levels low because it allows the plants to emerge, and also stops the fish getting out. Not nice finding them all crispy on the floor in the morning.

Good reasons, I'm not a crispy fish fan either.

In terms of the filtration capacity of the tank/filter system having emergent plants is actually more beneficial for water quality than having the extra volume of water that would fill in that couple of inches of air gap.

It sounds nonsensical, but emergent plants have access to aerial CO2 (400 ppm) and oxygen (21%), which are at levels many times greater in the atmosphere than in water. Floating plants have this as well, but they aren't rooted in the substrate. Emergent aquatic plants have an internal plumbing system that distributes this oxygen to the plant roots. This is from <Cyperus papyrus (http://tropical.theferns.info/image.php ... us+papyrus)>.



Roots are leaky structures and oxygen diffuses into the substrate, along with carbohydrates, that support microbial growth. It is in the in the rhizosphere, these fluctuating zones of REDOX, that both nitrification and denitrification can occur. It is the same principle that the old under-gravel filters used, but a lot more effective.

This principle is used a lot in warmer regions for phytoremediation in vertical flow constructed wetlands.

cheers Darrel

[Bas Pels]

If you have an emergent Echionodorus, a crossection looks much the same as the Papyrus above.

I never thought about the emergent parts aiding the roots with oxygen, but obviously, they must do so. Thanks for the idea.

[dw1305]

Hi all,

If you have an emergent Echinodorus, a cross section looks much the same as the Papyrus above.

I never thought about the emergent parts aiding the roots with oxygen, but obviously, they must do so. Thanks for the idea.

I've never looked at an Echinodorus leaf, but all rooted aquatic plants, with emergent leaves, will have a similar tissue, it is called "aerenchyma" (https://en.wikipedia.org/wiki/Aerenchyma), and they may also have large air channels or lacunae (https://cals.arizona.edu/azaqua/aquapla ... nments.doc). A really good example of lacunae is from the rhizome of the Lotus (Nelumbo nucifera) (below).



The rhizosphere oxygenation effect was something that I initially became interested in during my "day job", but it is one of the key concepts (Chapter 9. the "aerial advantage") in Diana Walstad's "Ecology of the Planted Aquarium" (https://www.amazon.co.uk/Ecology-Plante ... 0967377366), and it is also mentioned in Horst and Kipper's "Optimum Aquarium" (https://www.amazon.co.uk/Optimum-Aquari ... 3925916024).

A lot of the initial criticism of a plant/microbe/substrate approach to biofiltration was that plants depleted the oxygen from the water at night and weren't a significant source of nitrification when compared to the filter bacteria, but neither of these is really true.

Plants will deplete oxygen at night via respiration, but a lot of that oxygen actually comes from the internal tissues, where it has built up to high levels during photosynthesis, and the net oxygenation effect of plants is over-whelmingly positive.

This is from Faußer, A. et. al (2016) "Diurnal dynamics of oxygen and carbon dioxide concentrations in shoots and rhizomes of a perennial in a constructed wetland...." AoB PLANTS, 8. It shows how plants use the internally stored oxygen (produced by photosynthesis during the day) and carbon dioxide (net from respiration at night) for respiration at night and photosynthesis during the day respectively

.....Highly dynamic diurnal courses of [O 2 ] were recorded, which started at 6.5–13 % in the morning, increased rapidly up to 22 % during midday and declined exponentially during the night. Internal [CO 2 ] were high in the morning (1.55–17.5 %) and decreased (0.04–0.94 %) during the rapid increase of [O 2 ] in the culms. The observed negative correlations between [O 2 ] and [CO 2 ] particularly describe the below ground relationship between plant-mediated oxygen supply and oxygen use by respiration and biogeochemical processes in the rhizosphere...

Plant biofiltration is always plant/microbe biofiltration, and as well as directly taking up fixed nitrogen, plants create a much larger volume of substrate where nitrification can occur.

Aquatic plants have evolved in tandem with bacterial, archaeal and fungal symbionts for hundreds of millions of years and roots and rhizomes are actively leaky structures that create an oxygenated, nutrient rich, zone (the rhizosphere). This isn't an altruistic process, the symbionts create conditions which favour the growth of the plant, particularly by limiting the toxic effects of reduced iron (Fe).

cheers Darrel

[Bas Pels]

Thanks for this.

It looks like you are advocating keeping plants in aquariums, which is, however a statement I heartily agree to. I did mention Echionodorus not for nothing, it is a genus of plants I like a lot.

For instance, I got myself a few roots of E argentinensis in Uruguay, raised plants from them, got seeds and now I have a dozen seedlings of over half a meter high, growing n this half a meter of water. As far as I know, not many people, who declare themselfes plant lovers, try this.

[dw1305]

Hi all,

It looks like you are advocating keeping plants in aquariums, which is, however a statement I heartily agree to.

I want every-one to keep plants in their aquarium, not only because I like plants (I trained as a botanist), but because actively growing plants massively improve water quality.

For instance, I got myself a few roots of E argentinensis in Uruguay, raised plants from them, got seeds and now I have a dozen seedlings of over half a meter high, growing n this half a meter of water. As far as I know, not many people, who declare themselfes plant lovers, try this.

There are a few threads on the <"UKAPS forum" (https://www.ukaps.org/forum/threads/flo ... nts.51098/)> this is "....E. "kleiner bär" Jugle star No2 from Dennerle, it's a crossbreed from E. parviflorus, E. barthii and E. uruguayensis as far as i know".



cheers Darrel

[Bas Pels]

Mine are slightly larger, the mother has stems of a meter. Leaves the size of a dinnerplate

Unfortunately, due to severe depletion of the soil, I needed to redo the whole scape, and Sunday I emptied a tank, today I redid the soil, with a lot of clay (from the garden) and I intend to plant them again tomorrow.

I never took pictures of the whole.

Now the intention is to have some 20 plants groing in 1 tank, 140 * 65 cm footprint, hopefully each with 10 large leaves and a flowering stem. Such a tem can contain 100 to 150 flowers, flowering in the cours of some 2 months. I never see a second one, and I never saw young plants on them.

Anybody know a fish which likes to be among plants, and can withstand 5 C in winter and 25 - 30 C in summer?

[kvnbyl]

Additionally, why not give the fish more room to swim? why should they only have 60 gallons of room when there is 90 available? get an airstone or a circulation pump and fill it up! leave a little space in that tightly fitting cover.
There are pictures of many tanks, plants have nothing to do with them and they are not filled up and i just want to know if there a reason, something i might have missed
p.s. no offense but this question has nothing to do with plant roots or biofiltration, is there another reason?

[dw1305]

Hi all,

Additionally, why not give the fish more room to swim? why should they only have 60 gallons of room when there is 90 available? get an airstone or a circulation pump and fill it up! leave a little space in that tightly fitting cover

No fill the tank up near the top, unless there is a good reason not too.

I'll be honest the majority of fish I keep are small fish and they don't do much swimming away from the lowest levels of the tank, so the height of the water column isn't really all that relevant. Also, because I don't keep any fish that are active open water swimmers, I don't have tanks with large open areas of water, I use plants, like Ceratophyllum demersum, to fill in the "gaps".

p.s. no offense but this question has nothing to do with plant roots or biofiltration, is there another reason?

No offense taken, the only reason for mentioning the plants and biofiltration was that if you use the empty space for emergent plants, rather than water, it may actually benefit water quality and, in my opinion, better water quality is one of the major factors that leads to improved fish health.

cheers Darrel

[Jobro]

All my fish would be crispy, if my tanks looked like yours, Darrel

[Jools]

It is a thing of beauty though. Why would a fish want to leave? My son has been experimenting with open top tanks and it looks to work well so far...

Jools

[dw1305]

Hi all,

It is a thing of beauty though. Why would a fish want to leave? My son has been experimenting with open top tanks and it looks to work well so far...Jools

All my fish would be crispy, if my tanks looked like yours, Darrel

That tank belongs to Marcel ("Zozo"), unfortunately none of mine look anything like that good. He is a very enterprising aquarist.

He is also the owner of the

Hara jerdoni

in this post: "Hara surface feeding" viewtopic.php?f=9&t=46890 .

I have covers on my tank, although I've still had a few crispy fish (most frequently

Copella arnoldi

).

cheers Darrel

[N0body Of The Goat]

I keep my water levels low because it allows the plants to emerge, and also stops the fish getting out. Not nice finding them all crispy on the floor in the morning.

I've had a few "jumpers" over the last ~8.5 years, but the one I was most upset about was finding one of my five Euchilichthys spp. had jumped through a ~2.5cm gap in the glass sliders at one end of my 6-foot tank, around the time a bonded pair of Steatocranus casuarius had youngsters.

Despite their reputation of being tricky catfish to keep, especially in numbers within a single tank, the other four are still with me and must be getting very close to full adult size of ~18cm SL from being ~10cm SL when I got them just over five years ago... They are now longer than my Synodontis brichardi trio and could well be longer than my Synodontis budgetti.

[TwoTankAmin]

Everybody does things in the way that works for them. My tanks are spread out in two buildings and four rooms. If I did not use fairly tight fitting lids on them all I would have problems with evaporation and too much humidity in the house. In some tanks I would have jumpers. Of my 18 regular tanks (I have 2 more temporary ones up now), only 6 are planted (it used to be 12) and of those only three have plants in the substrate (a couple use plants in pots). All 6 have rock and wood mounted plants.

Most of my tanks are 80F+. Without lids the evaporation would be a real problem. The one thing I do know is oxygen levels are not an issue. I have bread Xingu plecos in warm water for years. I highly doubt if these fish would spawn were there not sufficient oxygen in the water and even if this happened, I doubt fry would do well with a shortage of oxygen.