I designed and built a fountain in my backyard using a horse trough that holds about 95 gallons of water. Adding little feeder fish seemed like a good idea at the time. Well, the fountain didn't quite work as planned, but a year later, the 14 goldfish are thriving and beautiful. On one end of the tank, I have two cement blocks, one on top of the other and on the other end, one cement block. I have large flat stones and a pot of horsetails on the single block, flat stones between the blocks and on top of the two stacked blocks. These are the cement (cinder) blocks with two large openings. My intent was to provide hiding places and separate zones for the fish and that the layered stones would help keep the water cool during the 100+ degree F summers. They did survive the first summer and nearly freezing temps of winter. Now that they're growing bigger, I think I should remove the cement blocks to open up more of the tank for them. What could I use in place that would still allow hiding places and something upon which to place the flat stones? I sadly realize that they'll likely outgrow their tank. Is there an alternative to finding someone with a pond suitable for my dear fish? Also, the pump keeps the water pretty clear but algae grows pretty quickly on the stones and sides of the tank. Is barley straw the answer? Thanks!