I have a 5g reef tank that has mixed corals - soft, lps and sps corals. I have been feeding the corals phytoplankton and putting a couple of grains of pellet food in there every now and then. Over the last few weeks, my tank has developed a hair algae problem. Also, my flame scallop passed away and I didn't catch it in time before it rotted away, so that could be the main issue. My plan of attack: 1. Get a turbo snail on loan 2. Siphon out some of the hair algae at the next water change. 3. Change my RO/DI filters out because TDS has reached 7. yikes. 4. If necessary, use a little GFO in a nylon bag in the sump. Id rather not use GFO with out delicate the system is. Not really asking for advice, just sharing my experience as the process continues in such a small tank. If anyone is interested in an in-depth discussion of reef chemistry in a small tank, let me know. I'll be glad to share.