Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
I would remove the marbles and Goldfish.
Set up a planted tank based on Platies.
You could use the marbles in a Goldfish tank, as decoration, on top of whatever substrate you want to use in a much larger tank. Or you could use a single layer of marbles on the floor of the tank. This would stabilize the poop and other debris so cleaning goes pretty fast. You will have to clean a LOT. Poop etc. shows up when you have a bare bottom tank. If you do this make sure you have a really large filter so there is plenty of room for nitrifying bacteria. Marbles are very bad housing for beneficial bacteria.