black slime in tank,

Question
my children have a small tank which holds about Ten gallons of water and there have a mixture of fish about Twenty five in totlal all small fisk. The problem is about two weeks after the tank has been cleaned the plants and rocks turn black,any ideas.

Answer
Hi John;

I need more information to be able to tell what's going on in there. Send me a followup question with answers to as many of the following as you can;

How long has the tank been set up?
Do you have live plants and they are dying/getting black or do you have fake plants and they get black?
How long have you had the fish?
What kinds of fish do you have? (Some fish are messy even while small)
How big is each fish right now?
How often do you feed them?
How long does it take for the fish to completely eat all the food from all areas of the tank after you feed them?
How often do you make water changes?
How much water is changed each time?
Do you vacuum the gravel?
What kind of filter does the tank have?
How often if the filter cleaned?

If you are unsure of the types of fish you have, send me a photo of the tank and fish with your followup question. All of this will greatly help. ;-)

At Your Service;
Chris Robbins