For both of my 120s, I dose 1-2 times a week with Mastergrow (100-150% dosage) and a daily dosing of Duplaplant 24. I also run Co2. I do not have any experience with Flourish, but I have never had a problem with Mastergrow. big D -- It's not a fish tank, it's a plant tank ... the fish are decoration. Check out my fish site @ http://home.austin.rr.com/ddaquaria