Oversized skimmer on undersized tanks

[Afrashz]

So what are the effects of using an oversized skimmer on undersized tanks? I am currently setting up a small frag tank, about 15 gallons when all said and done. I’ve been finding some decent deals online for “bigger” skimmers e.g. skimmers rated for 120 g max or so. What would be the effects of using these larger skimmers on smaller tanks like mine?

 

[Homebrewer]

I believe the thought is that it’s more difficult to dial in an oversized skimmer. Personally I always felt that over filtration and over skimming was a good thing. I remember a BRS video where one of the guys said he thinks a slightly undersized skimmer is a better choice and that made me re-think.

I haven’t done the “math” on it in a while, but I run an HOB skimmer and have always favored the Reef Octo brand. I got the larger version even though I could have gone with the smaller one i suppose, but I’ve never regretted going bigger. I guess what I’m saying is that as long as you’re in the ballpark, you’re probably ok.

So many other things factor in, like bioload, goals, etc. - so I’m sure you’ll get many opinions on this.

 

[Afrashz]

I believe the thought is that it’s more difficult to dial in an oversized skimmer. Personally I always felt that over filtration and over skimming was a good thing. I remember a BRS video where one of the guys said he thinks a slightly undersized skimmer is a better choice and that made me re-think.

I haven’t done the “math” on it in a while, but I run an HOB skimmer and have always favored the Reef Octo brand. I got the larger version even though I could have gone with the smaller one i suppose, but I’ve never regretted going bigger. I guess what I’m saying is that as long as you’re in the ballpark, you’re probably ok.

So many other things factor in, like bioload, goals, etc. - so I’m sure you’ll get many opinions on this.

Interesting, thanks!

 

[Gablami]

If your skimmer is very oversized (like you’re talking about), it may not skim properly. If you have a 15g tank and a couple fish, and buy a skimmer rated for 120g (which could hold 20 fish), you’re not going to have enough bioload and thus enough waste product to create the bubbles (head) to create skimmate. At best, the skimmer would skim very wet and inconsistently, at worse, you would not produce any skimmate because you can’t get the head to overflow into the cup.