BM Skimmer Ratings
 

I'm looking at adding a sump to a 40g breeder so I can get some more real estate being taken up by a Tunze 9004 skimmer and heater. The two skimmers I'm looking at are the BM Curve A5 DC and Curve A8 DC. The skimmer may also end up being used on a custom 75g as well in the near future. Currently no fish in the tank just mixed corals and shrimp but I would only stock a few smaller type of fishes like wrasses, dartfish, etc. so bioload wouldn't be really high in either tank. The A5 says it's rated for 50-150g and the A8 is 180-235g which seems excessive for what I need but I don't know how or if BM's ratings are highly optimistic. Any thoughts from BM owners?

I would go with A5. It's nice to have a big skimmer but you also need a big bioload in that case, that's the whole point of a bigger skimmer. There's also a good chance the pump on the bigger one pushes way more water than your return pump which means the thing will be re-skimming already skimmed water all the time. I actually have that problem a little bit and wish I went with one step down.

Yes, I agree. With sumps the tanks have water volumes of about 60 - 100 gallons and while the A5 covers this range according to BM's specs, I'm concerned that their ratings are being overly generous like a lot of other skimmers claims. I'm curious to see if people are running the A5 or A8 (or their non-DC counterparts the curve 5 & 7) on similar sized tanks. If the A5 will do the trick then I will be happy to save the extra $100 difference!