Its up to you. They say larger is bettr, but I have a 25 gal reef and its doing great. I keep a close eye on my water but other than that, its been easy. You will need a protien skimmer for sure if your planning on adding corals. your gonna be limited on what you can add so make sure to get what you want. larger fish will definately be out but there are some awesome small fish and inverts that are fun to watch. Think hard, if you really want a 40 gal I say go for it. And, this is the best bb around. They people here are friendly and most give great advise. Read, Read, and read some more. I know from experience that this helps. Good luck and have fun.
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