Hydra or something else?

[BK]

hi,

can brown hydra grow/surive in a bare tank, only tap water, an airstone, and sparce light? i have a brown fuzz that varys widely in size from .9cm strands to .5mm dots that has taken over a 5.5 gallon tank that i just began setting up and i think it could possibly be hydra but i'm just grasping at straws. i don't see any tentacles but i really don't know what hydra tencles look like.

thanks,
BK

[OrionGirl]

Brown fuzz sounds more like diatoms than hydra. Hydra have a short stump, that branches out into 5 or so smaller arms--think of a small oak tree in the winter, minus the twigs. They are flexible, and can move by somersaulting. Diatoms are microscopic, but will collect into a brown fuzzy layer which is easily swept away. Diatoms don't need light, and usually wear themselves out in a tank as they use up the available silica.