growth on rocks

Question
I have recently purchased two 10 gallons fish tanks. Though I have treated both
the same (including same types of fish) one is growing this cloudy white
substance on the rocks and paraphernalia ( castle, fake flora). I cleaned the
tank once after one of the fish ( I cant remember the name exactly
pleco...something they eat the algae that grows on the walls of the tank) died.
The sales person at the pet store could not tell me if the fish died because of
this growth and not being able to reach any algae or if the substance grew
because the fish was ill and not eating. Now the substance is back despite a
very thorough cleaning I have done some research and at first thought the
substance was a bacterial bloom but there was some conflicting information that
indicated the white substance would be free floating in the water and the
substance growing in my tank is not, it is on the rocks. So my question is what
is it and what should I do about it?

Answer
Hi Marisha;

A bacterial bloom in the water would simply make the water milky-looking. It could be bacteria colonies or fungi growing on extra food or decaying waste. If the whitish substance is fuzzy or hairy-looking it is a bacteria called "saprolegnia". If it looks slimy and spreads in a blanket type pattern, it would be a "slime mold". Either one calls for feeding less food to your fish and cleaning up the excess. Feed your fish once a day and only enough food for them to totally consume in 5 minutes from all areas of the tank.

One reason for uneaten food could be that the fish have lost their appetites. If your tank was recently set up it is probably still in the break-in period. Toxins will rise and cause the fish to feel sick so they don't eat as much as usual. Here is a link to my article about it;

http://www.xanga.com/Expert_Fish_Help

I hope things look better soon...

At Your Service;
Chris Robbins