This is a discussion on Weird fungus in tank. pls help within the Beginner Freshwater Aquarium forums, part of the Freshwater Fish and Aquariums category; -->
I bought a new 10g tank last week to keep a siamese fighter but now there is some cotton wool-like substance growing on some ...
Can you be more specific? Wha is it growing on exactly? Do you happen to have some Mopani wood in there?
Oh yeah sorry....no i dont have any wood in there yet, pet shop has no stock...
Its growing on the plastic top of my heater and i've seen it on my gravel too but im assuming thats from left over food. Im just puzzled as to why its on my heater...it looks sort of like a white floss. Dont know if that helps at all?
If it is whitish and cotton or fuzz-like in appearance, it is likely a fungus. You seem to be familiar with the fungus that will appear on uneaten food. That is one type, but there are a great many species of fungus. Some are basically safe, such as the one that grows on uneaten food. Some can however by highly toxic. Romad mentioned the wood fungus, and some of these can be deadly.
A photo of the "fungus" on the heater might help us, as I can't imagine why fungus would grow there. This could well be something entirely different.