Flow Requirements for 90g

I am stocking up on equipment for my new 90g that I will be setting up in a month or two. I already have a few powerheads for my 37g, but I will clearly need more.

I have read that I should have 35gph per gallon of the tank, so (35*90) 3150 gph of flow.

I have not yet purchased a sump for this tank, but I was thinking that a 30g would be the largest that could comfortably fit in the stand, with room for the external iwaki and possibly a top off bucket.

Getting back to the point, should I include the volume of the sump in this calculation? If so, I am guessing I should include the flow rate of the return pump. If I include the flow rate of the return pump, would it be reasonable to include the flow rate of the overflow? The flow rate of the overflow will be equal to the flow rate of the return pump..

 

gabbyr189 I also have a 90 gallon which I am currently a little further ahead than you are right now. I am not an expert but others can chime in as well, but your flow rate is really high. You should be shooting for 10-20x the gallon volume of your MD. Check out this link it will help.

Reef Sources Guide - Pumps & Moving Water

What type of 90gal did you get? Is it reef ready? Most reef ready 90 gal tanks have a flow rate of 750 gph. For your return pump you need to take into account the head of height pressure. Example my tank has a 750 gph flow rate my sump is 40gal under neath MD, my pump is a mag 9.5 which works perfectly because although the manufacturer says that it is rated at 950 gph it is really less when you include the Head pressure which mine is 5feet. This dropped my GPH to 750.

Go to this link. They have all sorts of calculators that you can use to help with what you need.

http://www.reefcentral.com/index.php?s=

 

By the way I have the mag 9.5 at 750 gph, dual JBJ Oceanstream Circulation Pump/Powerhead + Duo Wavemaker Kit 500 gph which once you read the article you will see that since they are on a wavemaker they are not running constantly. So I have a max of 2750 flow (if I don't run wavemaker) in my system which is more than 20x the volumen.

 

I probably should have specified that this will be a reef tank. In my current 37g reef I have surpassed a 60x turnover rate in powerheads alone. My corals could not be happier. I am just going replicate that.

 

Agreed. For FO or low-flow-loving softies and LPS, 10 - 20x is sufficient. Some LPS and most SPS should have at least 50x. Some members here are running in excess of 100x in their SPS-dominant tanks.

To answer your questions, no you would not include the overflow rate, as that is not water movement inside the DT, but rather, water flowing from the DT. However, you can include the return flow rate if your return lines are positioned to contribute to DT water movement. Some point them upward for surface circulation and therefore do not include it.

 

Interesting... Thanks, that is helpful. So by that theory, should sump volume also be excluded?

 

Depending on what ya wanna grow, LPS and softies, 30X seems OK, SPS 50X seems ok. My corals def loved my recent PH upgrade. I'm about 60X right now on a wave maker!

 

Yes. In fact, it's also typical to exclude the displaced volume. i.e. my tank is 29g. I have roughly 5g displaced by substrate and rock, so the volume for which I calculate flow is 24g. That would not change if I add a sump.

 

That makes sense. I have been meaning to calculate the actual water volume in my system. Though, I honestly have no clue how much rock I have. It is probably between 45 and 75 lbs. I believe I initially had 40 lbs, but I have added more along the way, several times. I have also added rock to my sump. Then there is the water in the skimmer and reactor. I am planning on chemically calculating the total volume. As a biology major, I have taken several courses in chemistry, including analytical chemistry. I just haven't gotten around to it yet..