a pair would work fine, you mean the nemo kind right? they are called occellrus.
a sump/WD is always best but if you have enough LR/LS in the tank a mediumish canister or HOB will do fine for mech.
ultimately i really think you will end up doing the 90 SW, it may take a few years but you will do it
the larger the tank obviously the easier it is for a beginner SW'er, but the more expensive. iwould think the 55 would be a good middle ground.
a berlin sump and fuge could work side by side but i don't think they can be incorperated into the same structure. like if you had a 10 sump and a 5 gal fuge with seperate pumps plumbing them to the tank i think it would work.
that's a lot lot of denitrifying power.
[FONT=arial,sans-serif][SIZE=-1]will a black [/SIZE][/FONT][FONT=arial,sans-serif][SIZE=-1]Ocellaris and an orange [/SIZE][/FONT][FONT=arial,sans-serif][SIZE=-1]Ocellaris clown breed?
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Ya do only a pair. As fair as filtration hook up a fluval 405 and you will be very happy with how clear your tank looks. I run a 405 on my 75 gallon and it is very clear. Invest in the tank before you invest in the livestock.