What's the deal with flow ratings?

Koralia Nano = 240 GPH
For aquariums up to 10 - 15 gallons

Zoo Med's Power Sweep = 160 GPH
For aquariums up to 30 gallons

Fluval 205 Canister Filter = 180 GPH
For aquariums up to 40 gallons

Anyone else confused with these ratings?...

I would think the flow rating of the Koralia would be enough for my 29 gallon tank? But it says for tanks up to 10 to 15 gallons?
Koralia has a flow rating of 60 more GPH then my main aquarium filter, so why is this only recommended for 10 gallon tanks? :huh:

Same with this Fluval 205..
I have dead spots on the surface of my water at the opposite end of the tank and all I have in my media baskets is basically nothing... I can barely get any surface movement from it unless I wedge a sponge behind the outlet to point it upward, even then still doesn't move any water at the other side of the tank.
I need a power head like the Korilia that will add movement to the under surface of my aquarium, something that will reach all the way to the opposite side with out being too large of a eye sore. my plants are collecting every piece of everything in my tank and it looks really bad.
I will be upgrading to a 50 gallon some time next year and I don't want to have to buy another power head just because I upgraded..

Will the Korilia Nano work for me?


I think flow rates for tank size might be calculated on the output diameter, larger diameter flows more water but not as strong of flow as a smaller output?
Just a thought..:headshake2:

My 400 GPH Emperor-400 was perfect for a 29 gallon tank.
I'm really thinking about installing it back on my aquarium..

Reefscape said:

The Hydor Koralia range of powerheads were designed with marine aquariums in mind, hence the flow rating and tank sizes....In a marine system you need a far higher flow rating than a FW tank...

Click to expand...

I was kinda thinking that since the descriptions only mention saltwater.
Wonder why they don't rate them for both? Do they have to pay for each letter on the box? lol