+1^ on everything said so far...anything to get surface agitation would help, lower the temp...idk if you have a heater on a walstad...but if possible, that might help as the colder the water, the more O2 in the water
TFB- Excellent advice...I had forgot about O2 in cooler/warmer water.
Maxthedog- I have found that there is always something happening in one of my tanks that has me going hmmm...and I've been doing this for nearly 20 years. Glad you found the AQ. Hopefully it helps your fish. Please keep us posted on how things are going.
Obviously the HOB and carbon are a temp solution - this is a Walstad aquarium after all. Thanks for everyone's advice. The lights are off on the aquarium, so we will see what tomorrow brings. Hopefully the fish will be swimming and not licking the glass lid for oxygen.
Well, the fish are all the correct direction - stomach down - and swimming around this morning. The lights haven't come on yet, but it looks like he cloudiness is reduced. I'll know more in a bit.
The $100 question - how long to leave the HOB on the tank and go back to "El Natural".
Glad the fish survived the night. I would keep the filter on for a good week and keep doing some water changes. Then pull it off and monitor it very closely. I know you hate having the filter on, but I would err on the side of caution. Sometimes these blooms can last just a few days, other times a few weeks.
Great job on what you are doing so far. You saved their wee fishy lives.
I would love to see some pictures of your natural tanks. I've considered doing the Walstad Shrimp Bowl many times and even a 20l as one. The thought of a self-sustaining ecosystem appeals to me on one hand, then goes against my current thinking on aquarium keeping at the same time. lol
I had/have a similar problem with my 55 dirt bottom tank. It hadn't been up and running a huge amount of time(3 weeks) and things went south. Fish all hanging at the surface and gasping for air. Large water changes made almost no difference. I threw and old hang on powerhead and things were INSTANTLY better. The canister filter was just not creating enough surface agitation to off gas the byproducts of all the decomposition going on in the soil bed and with the large piece of driftwood. It's been about a month since then and if I shut the powerhead off I'll notice the fish slowly spending more time at the surface after about two days, so obviously it still has an issue with surface gas exchange being insufficient. But I keep planting more plants and things will sort out eventually.