Hey people ive been reading up on both sumps and refs, but theirs not a thread which explains their differences or purposes.. other then to improve quality of water which is the obvious main reason or for extra storage space/to house a predatorial specimen even. Could somone or a few of you be kind enough.. to give me a run through and a couple answers to my questions listed below.... thank you thank you!!!! 1. Are they BOTH worth having? 2. Or can you have just one? 3. Which one would be the better choice? Another sort of off the subject question is... Im not sure wether to buy a skimmer i want to house corals polyps etc etc at some stage, but have read up that these devices take the required nutrients out of the water. True false? However im def interested in either purchasing or "making" a algae scrubber/prosphate/nitrite remover... im just drawing up a base plan in conjunction with my lid/lighting for that. So thats a definate. But even with nitrates ive read up also that a little is healthier then none at all, as corals like this?