Well my wild fish tank that I collected a few summers ago has diminished down to 2 occupants because of old age. A crayfish and a silver minnow of some sort. I moved them into a smaller tank as they don't need so much room. I completely cleaned the tank out and I cleaned the HOB filter completely I tore it into pieces and cleaned it all and re-assembled the filter. It is a really old whisper filter that takes the old Large Cartridges. I got an undergravel filter plate from probably the 1970's that I got for free from a local pet store that wanted to get rid of them. It was too large so I cut the plate and stuck it into the tank. I plan to burry it in gravel and power it with some extra air pumps that I have laying around. Basically I am using everything that I can to set up a new yet old tank with everything I already have. I just need gravel and fish. I am getting a new light bulb as I need one to have light in the tank as the light has been dead since I bought the tank used for $20 with a light, heaters, and a filter and the tank. I pitched the heaters as I did not like the looks of them. I bought a heater for another tank and realized because the heater was too long and not submersible I could not use it my 20 Long but it fits the 20 tall that I am setting up so it gets a brand new heater. Anyways I am looking for ideas for some occupants. I think a school of danios would be a good start. All suggestions should work with zebra danios. Also, I am debating whether a green gravel or natural gravel or black gravel or black with colored bits would be good. I have not decided so make a suggestion. Depending on cost I may be limited to natural colored gravel.