How much is too much flow?

[Teaching1974]

Hello, I am new to salwater aquariums and want to make sure that I do things right. I am afraid that I may be getting a little over my head, as I look into the posts on this site. My first question, I hope is a simple one, how much flow should I have in a full reef tank? I recently purchased a 180 gallon reef ready tank off of craigslist. The guy I bought it from gave me two pumps, that he used with his protien skimmer and sump, the protien skimmer, some lights; I believe metal halide, and his sump box. The pumps he gave me were bought specifically to drive the protien skimmer and sump box. I am looking at buying a 1/8 HP Dart Pump that will move 2400 GPH at 6' of head space. I am also looking at buying 2 or 3 in tank power heads that will move 600 GPH. Am I going to be creating problems for myself, or will this be OK? I am intending on having some corals, and if the lights truely are metal halides, even some of the harder to grow stuff. My main goal is to set it up so It requires as little maintenance as possible. If you need more information, I will try to answer any questions that you have to the best of my limited ability.

[quick_murdoc]

Welcome to TRT!

Here are a few things to think about, one you should have a good amount of flow with two powerheads that are moving 600 gal of water, but be advised that they will probably not move 600 but slightly less as most of the time the pumps are over estimated.

Second the pump that you will be using for the sump will be 2400 gph which might be a lot for your sump depending on the configuation. One thing to think about is the overflow, remember that you have to have a way to get the water that your pumping back into the sump. A one inch bulkhead has a max of 600 gph. So lets say you have two bulkheads in your overflow then you have a max of 1200 gph which is less then your pump is producing. So you have three options one reduce the output of the pump, two get a different pump or three re-plumb the tank. I hope that makes some sense.

Oh and as a side note most peopel like to have anywhere between 10-20 times the amount of flow in your tank. So if you have 180 gal tank then you would want somewhere from 1800-3600 gph of flow.

[Teaching1974]

So if I understand what you are saying, since I have two corner overflow holes (four total holes, two overflow two return) that are 1" each, then the most water I can move through the sump is 1200 GPH? Common sense says there is a limit as to what will go through the pipe, but I never even considered it would be a major limiting factor.

[Hop]

A rule of thumb is 3-5 times the tank volume through the sump per hour. So perhaps 900 gph would be a good starting point. The remaining flow should be made up through wide-spread powerheads or a closed loop. I run both and turn over about 50 times per hour through them.

[Teaching1974]

Thanks to you both. This has been very helpful. And thank you for the welcome message, quick-murdoc!