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Discussion Starter · #1 ·
I am new to NPT and have 2 tanks set up: 20galH with dirt from my yard and 1.8 gal bowl using organic miracle grow potting soil. The 20 gal started with the following 3mo ago:

anubius
crypt
green comboba
elodea
creeping charlie
lobielia
duckweed
Fish: 2 cories, 3 cherry barbs, 2 marble crays, cherry shrimp, snails

Ammonia and nitrites are 0 consistently. pH high at 8.2 and hardness at 250ppm. I put native rock in the tank as I want to mimic our native hard water in the chicago area. Water temp 77-81; no heater.

During the first week the creeping charlie and lobelia had rotted completely through at the stems bases and floated to the surface and eventually just disappeared. A few holes appeared in the anubias and the crypt lost leaves. I have no natural lighting available for this tank so I added a T5HO dual light hood and the anubius and crypte have hung in there but only grown a few leaves. The combaba and elodea have gradually rotted through but now grow as a dense floating mat.

The snails were proliferative initially but now only a few are left. The cray has multiplied and the fish seem very healthy.

I trimmed the floating mat -- one combaba string was 4' long! Cut them short and tried them in a 1.8 gal aquarium with normal water quality and pH 7.4, and 14W cool white fluorescent. They are still rotting away.

Any ideas?
 

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Welcome to APC!

Please tell us a little more about your tanks. How deep are the soil layer and cap of your substrate? Do you have any filtration or water circulation?

Anubias and cryptocoryne both grow slowly, and crypts often shed leaves when transplanted, "melting". So they are not acting abnormal.

Some crayfish are very destructive to plants, could they be munching through the stems at the substrate?
 

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Discussion Starter · #3 ·
Thanks for the quick reply - much appreciated.

20gal H: I have a small HOB fluval for filtration. The soil depth is about 1.5"-2" and the gravel cap is 3/4-1". The stem rot started way before the crays went into the tank and, though the crays snipped a few off, the stem bases turn yellow, translucent then floppy and brown and then give-way while the top stays green. Even as floaters the cabomba leaves continue to slowly rot away, frequently turning coppery first. The amount of brown mulm on all surfaces of rocks and plant leaves seems really high but I'm not sure what a NPT is supposed to look like -- looks pretty bad to me right now. Haven't done any real water changes -- just top-ups.

The stem rot process is repeating itself in the 1.8gal betta bowl that only has him and a few snails. this just has a little pump with waterfall effect (Tetra desktop bowl with LED but I skip those and put a 14W CFU cool white on it instead.)

The duckweed grows great in both tanks and I remove it regularly.
 

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OK, your soil depth is about twice what it should be, 1" is plenty in the 20 gallon and 1/2" would be good in the 2 gallon bowl.

This may be causing excessive anaerobic conditions in the soil, which would inhibit root growth especially in weakly rooted stem plants.

A properly set-up Walstad tank does not have brown sediment on leaves and stones. This suggests a failure of the cap, or disturbance by inhabitants. Sorry to pick on your crayfish again, but do they dig?

Duckweed grows best when there are a lot of nutrients dissolved in the water. In Walstad tanks we are trying to keep nutrients in the substrate. This also suggests that the cap has failed, allowing soil to release nutrients into the water.
 

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Discussion Starter · #5 ·
Oh, boy. Sounds like a total tear down then, right? When measuring the soil depth, is it packed down or just measured loose?

The crays are very good diggers so that's probably adding to the problem. I was planning a totally separate set up for them anyway so I should speed up that plan maybe.

I just set up another tank last night (20gal ex-high in sun room) and I made sure to cut back on the soil (1") and keep the cap smaller (1/2") but it got disturbed quite a bit during my clumsy efforts at filling -- do I need to tear down completely this one? Is there any way of correcting these tanks without tearing everything out? I only having floating plants in there right now but wanted to add more today by pushing them into the soil but that would disturb the cap again, right?

This is all proving way harder than I though. I've yet to set up one that the cap doesn't get disturbed someway-somehow but me, filter or inhabitants. :(
 

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On your new tank that was disturbed by filling, you should be able to (carefully) siphon out soil that is on top of the cap and hardscape. You can also add more cap. This may be a good idea, depending on what kind of cap you are using. Cap material with very small, mixed size particles (sand) should be thin (1/2") to avoid anaerobic substrate. Coarser material (gravel) can be thicker, to several inches.

A good filter with floss or sponges will also help remove particles in the water.

On a tank that has been set up for while, it is very difficult to remove part of the soil layer and then re-cap it without making a huge mess. The decision to tear down the tank depends on factors like having a good place to put the animals during tear-down and cycling, how bad conditions are in the tank, and how dissatisfied you are with it.

Before you decide to tear it down, try gently probing the substrate with a chop stick. If you release lots of bubbles smelling of rotten eggs (hydrogen sulfide), then you definitely have seriously oxygen-poor substrate. If the bubbles are odorless, then they are probably just CO2, which is good for the plants but not good for the animals in excess. Probing the substrate every few days to release the gas will help. Try planting some relatively fast growing plants with strong root systems: Echinodorus, Vallisneria, Nymphaea, etc. These plants have the ability to transport O2 to their roots, where it diffuses into the soil and creates a micro-aerobic environment around the root enabling it to function. Enough of these plants in a tank can help correct anaerobic substrate.
 

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Discussion Starter · #7 ·
ok, sounds good. I will siphon off the newly set up tank tonight and add a bigger cap.

I did a big filter clean and water change on the problem 20gal yesterday and will try the soil-poking tonight. In the meantime, I am setting up a few 10gal in case of emergency evacuation.

I'm definitely going to try the plant species you suggest first before a total tear down on the 20 but will add those right away to the new tank. I love the Walstad book but I'm learning a ton from your posts as well -- thanks so very much.
 
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