Concerns about soil in aquatic tanks

[evut]

I set up two Walstad type tanks recently. One is a large 200l tank, the other a 60l. Both have about 2-2.5 cm organic compost mixed with topsoil and a 1-1.5 cm layer of playsand and are heavily planted. Water quality has always been good in both tanks. The large tank is now suffering from algae quite a bit - short and long hair type, long strands form in the floating plants and short green fuzz covers most leaves. I do a partial water change about every 2 weeks.

I would appreciate if someone could let me know if something is wrong.
Why I'm concerned: in the large tank, which has been running since October, the newts are laying eggs and occasionally manage to pull a plant out. When I put it back in with tweezers, a large bubble comes out of the substrate. I tried poking the tweezers into the substrate in different areas of the tank and there is always a large bubble.

The smaller tank luckily wasn't inhabited yet when I broke a thermometer in it. I threw the water and substrate away and washed the filter and the plants. When I removed the substrate, I noticed it really stank - kind of like sewage (?) I'm not sure how to describe it...it was pretty disgusting. Is this normal?

Thanks for reading this! I am really worried that something is wrong with the tanks.

 

[methodik]

Hi Eva,

I also set up a Walstad-style tank (for my H. orientalis). It also occurs that when (re-)planting a bubble may show up. I guessed this was due to gases that develop from the plants roots and that get "stuck" under the layer of sand / gravel (or whatever you have on top of the soil). I am not a scientist, so maybe someone else has a correct explanation. However, I think, there is nothing wrong. Soil that has been laying in water should smell after a while I guess

Algae in Walstad types normally occur due to not enough planting. For example : My tank never had algae problems, but the newts rather "climb" through the plants than swim through the water. So I guess if you have newts that accept heavily planted habitats, you'd be fine with adding some plants that take up nutrients (for first help maybe Hornwort or Eloda spec - just thrown in, they will compete against the algae and probably win )

That is all I can say...I really have to read that great book again.

So far, hope this is correct and can help,

Jakob

 

[evut]

Thank you, Jakob.
The tank has lots of plants even though in hindsight I should have left the front without soil because there is a part with no plants (perhaps 1/3 of the tank could have been left without soil). I will try to think of a way to take out some of the soil now...any ideas? I suppose if all water was removed then it would be possible.
I have some floating hornwort but have to keep removing hair algae from it which is pretty annoying. I don't think it would be a good idea to have too much of it blocking the light so I regularly take a chunk out.

 

[Molch]

a bit of anaerobic gas would form in the substrate, and that's probably what the foul smell and bubbles are. I don't think that's all that bad - there's a bit about it in the Walstad book, I don't remember - but the H2S usually stays in the substrate and won't escape into the water column.

I've had occasional algae outbreaks too. Too much light can also do it. I did get rid of one algae outbreak by drastically reducing light to just a few hrs per day for about a month.