Just a note about blocking the overflow from small fish, I have an acrylic tank with overflow, and I use the plastic craft stuff to keep it covered. You can see, it does collect stuff, but I just brush it off with a toothbrush every week. And, the sheets are about 40 cents a sheet, and they are 8"X12" sheets, so you can replace them regularly with no problem. Mine are attached with a small black wire tie, but the suction will keep them in place for the most part. I use a Tidepool filter with a bio wheel underneath the tank, and it seems to work great. I have had the tank for about 11 years, but we did move 4 years ago, so I had to take it apart and start over when we got to the new house.
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