I set up a 20 gallon frag tank as a Quarantine/Observation tank and am planning on keeping new corals in it for 3 months to monitor them before adding to the display tank. I have about 20 LBS of live rock that's been in my sump for about a year. And a hang on back filter for filtration along with a power head. Im not planning on adding any fish to the system. What would be the best way to provide nutrients to the tank for the corals and to maintain the bacteria? I was debating on adding a small Yellow Canary Wrasse but was afraid that if I feed it a couple times a day , it may add more nutrients than the 20 gallon system could handle without doing a lot of water changes. Thanks for your help.