What is a good flow rate?

[PBearslax36]

If I have a 55 gal tank with a 20 gal long refugium, what is a good flow rate? 600gph, 400gph, 300gph, etc,? Thanks for your help.

[Loverotties]

The more the better 600gph.

[lizardarm]

yeah, i'd say the more the better. it depends on what you are (or are going to be) keeping in the tank.
more info would be helpful

[PBearslax36]

What kind of info would you guys like?

[lizardarm]

some corals (sps) generally need more flow than others (lps).

[yardboy]

In my 20 gallon tank I've got a 300gph return pump and an 850gph closed loop circulation pump. Seems about right since I've got sps corals in it.

[PBearslax36]

I am definately going to do LPS and Polyps.

Also, when I say flow rate (just want to make sure I am on the right page as everyone) I am talking about the gph of the overflow going into the fuge, then the gph of the pump going back up to the tank, right?

[Cosine]

the flow rate is the flow through the tank
the flow through the overflow will equal flow pushed by the return pump. add that to the flow provided by CLS/powerheads

[PBearslax36]

So where would I put the overflow box and the return hose?

[craigGP]

Originally Posted by Cosine

the flow rate is the flow through the tank

think of it as total GPH moved within the entire system. for the sake of the inhabitants, there should be a total flow rate of "x", depending on the inhabitants. the total flow rate is made up of several components. first, there is any powerheads located within the tank. second, there is a closed loop system, in which water exits the tank, goes thru a pump, and back into the tank. it is a "closed" system, in other words, no water can leak out. your filstar filters are closed loops, with a specialized section for filtering media. finally, there is water being moved thru the sump/refuge that adds to the total flow rate.

Originally Posted by Cosine

the flow through the overflow will equal flow pushed by the return pump.

the overflow passively moves water out of the tank. there is no pump pushing water out. as the return pump in the sump fills the 55 gal display tank, the overflow box lets the water leak out of the display tank back to the sump before the display tank fills to the top and spills. the rate that the water "leaks out" thru the overflow box is equal to the rate that the return pump fills the tank. its like the second drain your bathtub has about 2/3 the way to the top. if the water fills to there, it leaks out that drain so the tub doesn't overflow. the rate that water goes out the drain is dependant on how fast water is added to the tub. if it is just dripping in then it will just drip out the drain. there is a maximum rate that any given overflow will allow water to "leak out", which should be clearly stated on packaging/advertisement/owner's manual. i would get an overflow box that can handle 30% more than you intend to put thru it.

Originally Posted by PBearslax36

So where would I put the overflow box and the return hose?

that is up to you. the overflow is frequently put in the middle/back of the tank (as the center bracing allows) and return comes into an end. many people split the return line into two lines after the pump. adding a "Y" connector allows for water to be returned to both ends of the tank for better circulation. there is nothing written in stone what is best, but i prefer splitting it to stir both ends of the tank. i split my return line with a SCWD, which is a wave making contraption that takes a single input of water from the return pump and alternately sends it out one of two exiting return lines into the tank. the SCWD slows the output by about 50% in my estimation, so you would want a more powerful pump to keep the flow rate thru the sump at the level you desire. i use a Quiet One 4000 pump that is rated just over 1000 gph with 0 head. at 4' head, the pump drops to 775 gph (according to flow chart from manufacturer). add in the SCWD slowing the water by about half and the resistance of water flowing thru a pipe, thru bends, etc. and i'm probably down to about 350 gph. that is good for my application because i have a refuge that i want to export nutrients and i have additional flow from other sources in the tank.

Originally Posted by PBearslax36

I am definately going to do LPS and Polyps.

this means that you will want some areas with lower current, as some lps don't want high flow. i don't know the rule of thumb for softies and lps, but know it is not as high as the needs of sps corals. in other words, you probably will not need to move 57x your tank volume in gph like tankboy is. i'd guess that a total flow rate of 1100 to 1500 gph would be sufficient for what you are planning. i'd rely on others and searches for specific recommendations on total flow rates needed for the lifestock you plan to keep.

sorry for writing a book and i hope i didn't over-explain things you already know.

craig

[PBearslax36]

Thanks Craig. I am learning more and more. I have a question about the total flow you were talking about before. Here is what I have:
2 Filstars at opposite ends. Each is rated at 300gph.
2 maxi jet ph in the top back corners of the tank. Each rated for 230gph.

So is my total flow 1060gph?

[craigGP]

so far it is. when you get your sump set up, it will be added too. if you take the total flow and divide it by the number of gallons in your system, you will get the turnover rate, or number of times the total volume of the tank will be pumped per hour. this is usually the number that is discussed when the "rule of thumb" of total flow is discussed. you currently have just under 20x (1060/55=19.3) turnover rate including only the tank volume. people will throw around numbers that are targets to hit when determining total flow rate for a tank. off the top of my head, i don't remember those numbers, but i'm sure its out there if you look.

craig

[PBearslax36]

So if i wanted to do a closed loop would i be able to do this. my filstar canister have a pvc tube sucking water in to the canister, then pushing it back up into the tank and out through a spray bar. would i be able to just leave the tubes and everythign else in place, disconnect my canister filter, and replace it with a mag drive pump?

[craigGP]

you got it. make sure the mag drive can be run externally. i think most of the larger ones can.

craig