My 29g FW
tank 'had' a fairly rapid 'growing' white fuzz on the gravel. I broke it down, cleaned everything, rebuilt it - and now - five weeks later - IT'S BACK !!!!!!
I soaked the gravel in bleach, scrubbed the plumbing - it's making me crazy.
The stuff appears to be 'rooted' to the surface of the gravel. It will generally take some gravel with it when pulled.
Fishies seem healthy. No other apparent problem. (the teardown did remind me not to overfeed).
Need brilliant idea. Will take not so brilliant suggestions as well.