Two weeks ago I set up my 20 gallon walstad aquarium. About 3 days ago I stared seeing some algae growth, and my plan was to move in snails and amano shrimp. But I checked my water parameters and they were off the charts for both ammonia and nitrites. So I decided to do a water change and wait to add the shrimp and snails in. Now my aquarium is completely covered in brown and green algae, and I am worried it will kill my plants. What should I do?
Long story short, do a bunch of water changes over the next few weeks (as in at least 1 a day) and reduce your light cycle to 4 hours a day.
There is a lot of misinformation on Walstad tanks (personal opinion). They get advertised as no maintenance tanks but I have found they need just as much maintenance as any other similar tank. One thing to keep in mind is that a Walstad tank has a nutrient rich substrate just like aquasoil. Depending on what was in your dirt, it almost certainly has even more nutrients then aquasoil as well. Aquasoil tanks need a water change every day for the first week they are setup, every other day the second week, 3 times in the third week, and 2 times in the fourth week. Thereafter once a week and each of these should be at least 50% water changes (I prefer 75+%). A Walstad tanks needs the same. The way you wrote your post it sounds like you haven't been doing much in the way of water changes?
You can also run a filter (if not doing so already) and run activated carbon in that filter at least till you can get your snails and amano shrimp in the tank. Do you have floating plants? If not consider them as they can help reduce the nutrient release.
In the immediate future you will also want to do as much manual removal of algae as possible. Hopefully this is helpful.
