Plants in the low KH aquarium

[raymond82]

Hi,

Here's another pH question!

Recently I was told then when keeping fish in a low KH aquarium, it is best to keep the aquarium with few plants and away from light to avoid pH drops.

My answer to this would be that in low KH water with low conductivity there is less need to worry about pH swings and that frequent water changes would also reduce the risk.

Would you agree with this answer? In other words: can I put as many plants as I want in my low KH aquariums?

Thanks!

 

[dw1305]

Hi all,

can I put as many plants as I want in my low KH aquariums?

Yes you can. The perceived problem is with pH scale. When you have low conductivity water with little carbonate buffering pH is a meaningless measurement.

Recently I was told then when keeping fish in a low KH aquarium, it is best to keep the aquarium with few plants and away from light to avoid pH drops.

Changes in pH which are caused by changes in the CO2 or O2 content of the water don't change the alkalinity of the water, but just pH. Soft water with photosynthesising plants will naturally have huge pH swings, it doesn't effect the inhabitants.

This is from Rocha, RRA.; Thomaz, SM.; Carvalho, P. & Gomes, LC. (2007)
Modelling chlorophyll-α and dissolved oxygen concentration in tropical floodplain lakes (Paraná River, Brazil) Brazilian Journal of Biology 69:.

The only problems you have is that some plants won't grow in acid, nutrient poor water, Vallisneria spp. don't do well for example. Most "low light" plants - floaters, mosses, ferns, Echinodorus spp., most Cryptocoryne spp, are fine, and some plants such as Tonina, Brasenia, Eriocaulon etc are only happy in soft acid water.

This is a tank with rain/RO water and a couple of Parosphromenus "Sentang". I haven't measured pH or dKH, but it is about 40microS conductivity.

and this one is 100% rain-water and about 100 microS.

Fish and plants are doing fine, and they are long set up stable systems.

cheers Darrel

 

[gerald]

I sometimes put a little aragonite mixed with clay into plant pots in soft/acid tanks, so they can get some Ca, Mg, and HCO3 via roots without adding much hardness or raising pH in the water above. (Actually I'm not sure if roots can uptake HCO3 - anybody know?) Gentle aeration is usually enough to minimize pH swings. Plants & algae cause pH to rise (by depleting CO2 in still water) but they won't cause it to drop below whatever it would be at equilibrium with air. It's mainly acidification by bacteria (both decomposers and nitrifiers) that causes pH in aquaria to keep dropping, and that will occur with or without plants.

 

[dw1305]

Hi all,

little aragonite mixed with clay into plant pots in soft/acid tanks, so they can get some Ca, Mg, and HCO3 via roots without adding much hardness or raising pH in the water above

A small amount of clay (to add CEC) and oyster shell grit etc for some dKH is probably a good approach. I always have the opposite problem of trying to remove dKH, as even our rain-water has some dKH (all the geology is limestone here (Bath, S. Cotwolds, UK)). We had a good post on this a while ago, with thanks to Gerald and Jaafaman <http://www.apistogramma.com/forum/index.php?threads/ca-mg-and-hardness.11556/#post-62828> and there is this page via the ever erudite "Skeptical Aquarist" - <http://www.skepticalaquarist.com/alkalinity>.

Gentle aeration is usually enough to minimize pH swings. Plants & algae cause pH to rise (by depleting CO2 in still water) but they won't cause it to drop below whatever it would be at equilibrium with air.

Point taken, if you have a large plant load in deep tanks you may find that pH levels have fallen before lights on, even with some water movement.

It's mainly acidification by bacteria (both decomposers and nitrifiers) that causes pH in aquaria to keep dropping, and that will occur with or without plants.

I'm pretty sure that you can ignore bio-acidification <http://www.skepticalaquarist.com/bioacidification> in planted tanks, unless they are really neglected and have a huge mass of decaying vegetation.

cheers Darrel

 

[raymond82]

Yes you can. The perceived problem is with pH scale. When you have low conductivity water with little carbonate buffering pH is a meaningless measurement.

Thanks Darrel, this is the answer I expected! Very nice tanks you have by the way, for mine I'm not gonna put that many plants since I don't have much light. But at least I don't have to worry about it, I like plants in the aquarium because they look good, improve the water and also provide a lot of hiding space and cover. I usually only use java fern, Echinodorus, cryptocorine and anubias but I checked and I also really like the Tonina that you mentioned.

I sometimes put a little aragonite mixed with clay into plant pots in soft/acid tanks, so they can get some Ca, Mg, and HCO3 via roots without adding much hardness or raising pH in the water above.

That's very interesting, I have to admit that I neglect my plants a little bit in terms of nutrition etc. Usually they're in a state where they don't die but they also don't grow with me, my main concern is getting the water right for the fish. However I would love to find a balance and make both happy...

Gentle aeration is usually enough to minimize pH swings.

Since I use air sponge filters there's always some aeration in the tanks

It's mainly acidification by bacteria (both decomposers and nitrifiers) that causes pH in aquaria to keep dropping, and that will occur with or without plants.​

I'm pretty sure that you can ignore bio-acidification <http://www.skepticalaquarist.com/bioacidification> in planted tanks, unless they are really neglected and have a huge mass of decaying vegetation.

I guess any problems with bio-acidification can also be accounted for by doing regular water changes?

 

[gerald]

"... unless they are really neglected and have a huge mass of decaying vegetation."
Hmmm ... never occurred to me that other people's tanks might NOT be like mine.

 

[raymond82]

My aquariums have quite some leaves in there, some of it decaying. I am however curious to see what a "huge mass of decaying vegetation" looks like

 

[dw1305]

Hi all,

"... unless they are really neglected and have a huge mass of decaying vegetation." Hmmm ... never occurred to me that other people's tanks might NOT be like mine.

Yes, I think it is really a left over as a worry from when people didn't change their tank water, and "aged tank water" was thought to have all sorts of magical properties. I originally gave up fish keeping in the 1970's because I used to kill my fish on a regular basis and it really upset me, but looking back on it, based on the "best practice" in the literature which was available at the time, it is amazing they lasted as long as they did.

My aquariums have quite some leaves in there, some of it decaying.

This is slightly different, when a tree shed its leaves it withdraws all the sugars and proteins from them. This is why leaves change colour in the autumn, the chlorophyll (protein) is withdrawn removing the green colour, and the colours of the anthocyanins and other secondary metabolites can be seen. The leaf will have already stopped photosynthesising, so the stores of glucose and starch will have all ready been utilised, and only the structural carbohydrates, the cellulose and lignin, and the secondary metabolites that can't be re-cycled, will be left.

These structures are resistant to microbial decomposition, so that they can't produce a rapid bloom of bacteria that will deplete oxygen and carbonate hardness.
Freshwater biologists use the term BOD - "Biochemical Oxygen Demand" to express the total demand for oxygen from the biota, decomposition and any chemical reactions (e.g. the rusting of elemental iron to rust ~ Fe to Fe2O3·nH2O & FeO(OH)·Fe(OH)3.). Unfortunately even in a lab. it isn't that easy to quantify BOD.

There is a bit more explanation here, it is ostensibly about oxygenation, and I wrote it for plec keepers, but the bits about biological filtration are relevant to most fish keeping : <http://plecoplanet.com/?page_id=829>. This is a thread on "Planet Catfish" that covers BOD and wood <http://www.planetcatfish.com/forum/viewtopic.php?f=4&t=35930&hilit=+wood+bod>.

cheers Darrel

 

[dw1305]

Hi all,
I should also have said that even in the

huge mass of decaying vegetation

scenario, problems are likely to come from this blocking the filter and impeding water flow, rather than directly from the BOD of the decaying vegetation.

cheers Darrel

 

[raymond82]

Thanks Darrel, I'm not worried about the decaying matter in my tank anymore. Anyway it's not many leaves and I do regular water changes. The article on plecoplanet is quite interesting, I used to have a tank with fry and they would always be breathing quite rapidly. I never understood what it was, the fish seemed to otherwise be doing fine and I didn't see any deaths. I recently traded all these fish, but in retrospect I can think of some reasons that popped up after reading these threads and the article on plecoplanet.

I usually use these types of filters:

I have been wondering lately about whether I'm using them correctly. I place them such that the air outlet is at the water level so it moves the water properly. However, I never see actual water flowing out (also not when I raise the outlet to above water level) I thought that's how it meant to be but recently I visited someone who uses Hamburger matten type filters and he had quite impressive water flow out of the outlet.

However, the filters do seem to pick up quite some dirt, which made me think that water is flowing through the filter. Referring to the fry that was breathing rapidly, the filter in their aquarium used to pick up the most dirt (from decaying plant matter). Yet, since I didn't see water coming out of the outlet I have no way of knowing whether the filter is actually doing anything... Actually, since the filter was still moving the water surface I figured oxygen levels couldn't be the problem...

 

[dw1305]

Hi all,
I haven't used air powered sponges for a long time now, although I used to use them and I know a lot of people with fish houses etc use them, so hopefully Steve Chesters or Mike W. can give you an answer. When I started keeping fish again I had a lot of maxi-jet pumps and sponge (left over from our landfill leachate and hydroponics work), so I just made use of those as sponge blocks or HMF's and as pumps for over-tank trickle filters (again based on house guttering left over from earlier work).

Planted wet and dry trickle filters are the gold standard for biological filtration, but my wife didn't get on with the noise at home and an HMF was a bit intrusive, so I started buying 2nd hand Eheim canister filters. Now I use a Eheim canister filter and a sponge filter on every tank, so they are massively over-filtered. I don't think it makes much difference for Apistogramma, but fish like Hypancistrus are very unforgiving of any drop in oxygenation.

cheers Darrel

 

[gerald]

If you lift the outlet of an air-driven filter just barely above the surface and you're just getting bubbles with almost no water flow, then either the media or tube is clogged, or the airlift tube is too short or too wide for the volume of air it's receiving. Sponge filters with short wide pipes need a lot of air to work well. Narrower pipes are better if you prefer a small trickle of air. You'll get maximum water flow (at any air volume) if the pipe ends just below the water surface.

 

[raymond82]

I would love to have Eheim cannister filters on all of my tanks but I'm afraid that would mean to much of an investment now....

Thanks Gerald, I usually use a small amount of air and the pipes are indeed quite thick... That means I would either have to increase the airflow or somehow decrease the thickness of the pipes. I think I'm gonna try doing the latter since I don't think I have enough pumps to increase the air much, and I do prefer having a small trickle of air. I clean the sponges regularly so that shouldn't be the problem.

I'm wondering now, looking at all the spongefilters we have (I'm surrounded by them), whether they're actually filtering water or just blowing out air bubbles at a low rate... I'm going to have to do some testing!

 

[raymond82]

If you lift the outlet of an air-driven filter just barely above the surface and you're just getting bubbles with almost no water flow, then either the media or tube is clogged, or the airlift tube is too short or too wide for the volume of air it's receiving. Sponge filters with short wide pipes need a lot of air to work well. Narrower pipes are better if you prefer a small trickle of air. You'll get maximum water flow (at any air volume) if the pipe ends just below the water surface.

Tonight I finally had time to have a look at all my filters and none of them was working properly! One way or another they were all clogged, either by the pipe blocking the air inlet or because of broken regulators.

I used Gerald's comments to adjust them all properly and now they're working like a dream!

Thanks!