my recommendation is to get the biggest tank can fit/afford then let it cycle while reading up on R2R , then start your journey, not only will it give you more stability but your will have the room to grow into. people often make the mistake of thinking they can nano reef (which is harder than normal reefing) then when they have a crash , boom they quit. Then figure they can get back in with a bigger tank for more stability , so they spent double the time/ money and now have spent money twice. I suggest everybody also gives the tank a good 2 years to settle into its zone. Dont freak out about every little thing until after you've been up a few years , things swing a lot in the beginning . Currently running a 80DT with 40GT and 30 FT all plumbed into a 40 breeder sump. Total volume is like 175gal , I ran nano tanks for ever and they are a whole diff animal than a larger reef system