how much GPH with powerhead and HOB filter

[twoodrough]

I have been running a 10 gal FOWLR for a few months. I have LFS do water tests and all had been good so far. I lost an emerald crab early on, but got a another one later on and he is doing well.

I am in the process of setting up a 20 gal. Given my limited storage space for water and my budget for fish and critters and supplies, this was the perfect size for me.

My plan is to have 3 fish (BW ocellaris I have now, a royal gramma, and a purple firefish). I have a peppermint shrimp now, a snail, and the emerald crab. I may or may not add other critters down the road.

I will never do a full blown reef tank. I am not fond of the look of them, too busy. But, once I get the fish I want and have maintained for a while, I may try some low light easy to care for corals.

I do 10% pwc each week. I use a couple water additives to keep my params in line. I feed once a day skipping once in a while. I use the HOB for phosguard, purigen and a sponge. I have been using a Koralia 240 in the 10 gallon. I have about 8.5 pounds of live rock, and will add a bit more when I upgrade.

I have ordered a 200 GPH HOB filter and I will use a Koralia 425 power head. Is there any reason for me to run more powerheads? I am thinking the fish might not like all the water movement, and if I am not going reef, I don't need much more.

 

[Ranette]

I am also still confused as to how much water flow is needed in my 40G FOWLR. I'm currently housing a neon blue damsel, a 3 striped damsel, an Oc clown, a scooter Blenny and a cleaner shrimp. I've got a canister filter that is showing 300 GPH output, and have two power heads that can output as much as 450 GPH each. Right now I'm not running both power heads as the clown especially seems to "struggle" with that much water flow. Am thinking about downgrading to get three power heads that produce about 150 each and placing them so there are no dead spots in the tank. Any advise or comments would be greatly appreciated.


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[Sniperhank]

It can be a difficult question to answer. You don't want food or poop to settle in your tank and become a nutrient problem down the road.
Depending who you ask, you can do 10x the water in your tank...so 400gph should be good! While others say much more as you would aim for 40-50 at times for a reef environment.
With that said, I usually say use two powerheads so you can create a more 'random' flow pattern in your tank to help simulate the natural environments better AND to help lessen the chance of having any dead spots.
After that, it is all about adjusting to what works. Point them at each other, point one up to get more CO2 exchange...so on.

EDIT: Though the GPH from HOBs does count, I usually try not to count them as it is not very effective as it simply is a water fall back into the system itself. Compare this to a return from a sump for example with a large pump shooting water directly in the water column itself, just like a powerhead would.

 

[54seaweed]

In my 40b I run 2 650's on either end and a 450 in the center , been debating on changing out the 2 650's with 2 950's , the more flow you have the better off you'll be
my predators like the stronger flow ,as they seem to play in it

 

[Beej1254]

I like the idea of more smaller power heads versus less but more powerful ones. I sometimes have up to 45x gph flow in my tank. Other times I drop it back to 15x. What I hate about it all and what I (think) I'll like about having more power heads is coverage. I want flow to get to more places steadily without having to blast the tank to reach everything. I have a 2ft deep tank and I've created water vortex from the sand bed up to the power head before with how high I've had it set. Not cool especially because it just makes things collect on the sand bed below the PH.


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