Skimmer sizing

[SeaKing]

I have read two competing views on sizing of your skimmer - so say to oversize, others say that an oversized skimmer will not have enough dissolved organics to function properly....  I am looking at getting a 250g skimmer for my 90g + 30g sump with a view to grow that to dual 90G with a 60g of sump and refuge. Should I wait to get the oversized skimmer?

[bt]

What I've read is that most skimmers are over-rated, or rated for a very lightly stocked tank of that size.

So a 250g rated skimmer would be good for a lightly stocked 250g FOWLR, but maybe only 110-120g for a heavily stocked reef tank.

Here's a description from Tunze for their skimmers:

Low sensitivity, no reductions
In leather coral aquariums with long-polyp corals and anemones, for example, the load of dissolved organic matter may be higher, sometimes it may even be vital. The DOC Skimmer can be used for the recommended aquarium volume without reductions.

Average sensitivity, 40 per cent reduction
A medium organic sensitivity is usually found in mixed aquariums inhabited with leather and stoney corals (LPS). Filter-feeding animals, sponges, et cetera, are found there frequently as well. For these aquariums, a reduction of about 40 per cent of the skimming capacity is calculated. Thus, a DOC skimmer for 1,000 litres (264 USgal.) should be used for a tank with a maximum content of 600 litres (158 USgal.).

Increased sensitivity, 60 per cent reduction
Aquariums with primarily small-polyp stoney corals (SPS) require an especially high degree of purity. They should have no load of phosphates or nitrates worth mentioning. Good oxygen saturation and very clear water are the pre-requisites. In this type of aquarium, the DOC skimmer is frequently used as a "stand-alone solution", thus a model for 1,000 litres (264 USgal.) should be used for a tank with a maximum content of 400 litres (105 USgal.).

High sensitivity and high load. 70 per cent reduction
Hard coral aquariums (SPS) with a high population of fish require an extremely high skimming capacity. The skimmer has to ensure the degree of purity for hard corals in case of above-average fish stock; as a "stand-alone solution" an especially high performance is required. Thus, a DOC skimmer for 1,000 litres (264 USgal.) should be used for a tank with a maximum content of 300 litres (79 USgal.).

[Cheebs]

I agree with what bt said. Although perhaps not the best example, I've got a 220g rated skimmer for my 40 gallon tank, and it pull like a beast, but I do have a decent bioload. You wouldn't NEED to go way overboard, but I think 250g will work just fine for you. A lot will depend on the quality of skimmer as well.

[Hookup]

My last was rated at 700gallons. 

My current at 900gallons.


Thinking of running both.

On my 180display + 150sump...  Heavily stocked.



And to be clear, FOWLR doesnt need the water quality that most reefs do, so a smaller skimmer is ok as you can have dirty(er) water... Corals do not really have any significant bio-load on a system.  I didn't want you to think corals are dirty and therefore add them means adding a big skimmer...