What's Monster fish ? Anyway my bf used to have a freshwater tank which he covert to marine tank, just like you, soon he started hanging Reactors, skimmer, hang this Hang that, such an eyesore, in the end bought a new tank set with sump. I say, if possible do it write from the start get a tank with sump, it pays for itself in the Long run. However if you have to really settle for sumpless, must gets FOWLR: refractometer, hangon protein skimmer, wavemaker,liverock for denitrification , but if you don't mind the eyesore or have a place to hide marine blocks, they're really good for hosting beneficial bacterias, LPS/ soft coral: refractometer, liverock, hangon skimmer, phosban reactor, biopellet reactor, chiller , wavemaker, test kits : kH, pH, nitrate, phosphate at least . Good luck Sent from Singapore Reef Club mobile app