Black algae in a goldfish aquarium
I replaced my 60 liter with a 200 liter aquarium in December. I have hard leaved plants in my aquarium, so the 2 catfish will not eat all plants. Now black pustules and threads grow on the leaf edges. What is this? Besides the 2 catfish, I also have 12 veiltail goldfish (5 cm).
the pustules and threads are probably black spot and/or beard/brush algae, which biologically belong to the red algae. In this case it is advisable to lower the phosphate and also the iron levels. 12 goldfish are a considerable burden for the aquarium, even if they are still small. You should provide at least 400 - 500 liters in the long run, as the fish will grow.
Dr. Bodo Schnell