I have a Bio filter and a small Bog filter which will I will be making bigger next Spring. I don't have a bottom drain. I just empty it every Spring and spray it with the hose. It's a weekend project when we get a hot Spring day. I didn't need a skimmer, we don't have any trees, any thing that does get in there, I have a skimmer net to scoop it out with. I only have 4 koi, the rest are comets and shubunkins.