GPH Supported by built in overflows.

jamessp01 · 12-30-2007, 09:55 AM

Hello,

I recently ordered a tank (glass 120gal, 48x24x24). I was not really thinking about flow rates when i did it. The tank comes with 1 corner overflow, i didnt think to inquire about the size of the bulkhead hole.

Im sure lots out there have glass tanks though and have some experience with the volumes supported.

I was planning on running about 900gph through the overflow. (Iwaki MD55RLT at about 12 feet of head.) Will one "standard" overflow support that?

thanks

fish.freak · 12-30-2007, 09:59 AM

may be a bit much, but im not sure. is it a standard AGA?

jamessp01 · 12-30-2007, 10:07 AM

Quote:

Originally Posted by fish.freak

may be a bit much, but im not sure. is it a standard AGA?

Yep.

crvz · 12-30-2007, 10:24 AM

That's probably too much flow. I imagine it's going to have a 1" drain, which is limited to about 600 gph.

jamessp01 · 12-30-2007, 10:34 AM

Quote:

Originally Posted by crvz

That's probably too much flow. I imagine it's going to have a 1" drain, which is limited to about 600 gph.

ok, so a 1" hole is limited to about 600gph, good to know. But that leads me to the question of how are people doing this when Im reading about turnover rates of 30x-100x tank volume?

Im a bit old school, i had a small reef about 15 years ago, think back then I think flow was recommended about about 5x tank volume. (been itching to get back into it ever sinse, just been waiting for the right time)

I dont really have a problem with 600gph, the skimmer/chiller are rated for less than that I beleive, so it should be sufficient.

fish.freak · 12-30-2007, 10:43 AM

either a CLS "closed loop system" in addition to the return, or powerheads like tunze or vortechs

kwjones · 12-30-2007, 10:47 AM

30-100x turnover rates in the display tank are achieved by closed loop systems or power heads like Tunze.

Personally I wouldn't want more than 3-5x turnover in my sump. It gives more time to for stuff to settle out of the water before getting pumped back up to the display.

jamessp01 · 12-30-2007, 10:57 AM

Quote:

Originally Posted by kwjones

30-100x turnover rates in the display tank are achieved by closed loop systems or power heads like Tunze.

Personally I wouldn't want more than 3-5x turnover in my sump. It gives more time to for stuff to settle out of the water before getting pumped back up to the display.

ok, that makes sence, those big numbers are just circulation inside the tank.

I'm also glad to know that it sounds like ill be OK on the rate to the sump, was not liking the idea that the first item I bought for a new reef setup was also my first mistake.

Im unsure where im going to end up with intra tank flow as of now, im planning on some sort of high volume, low pressure movement, or maybe just a wave box with some sort of spray bar behind the live rock to try and elminate dead spots. Planning on haveing a couple seahorses in here so flow cant be extreem.

Fat Tony · 12-30-2007, 10:57 AM

does it have one hole or two, if two, use both as drains so it gives you the capability of 1200gph. then go over the back with your return/returns...

kwjones · 12-30-2007, 11:03 AM

Yeah, if it's going to be a seahorse tank, you really don't want a lot of velocity in the tank. You can slow down the amount of water going back up to the display tank by splitting the return line and putting a ball valve on the split that drains back into the sump.

tdwyatt · 12-30-2007, 11:10 AM

Welcome back, James! I hope your tank does well, it's good to plan ahead, always a good sign for your develpoing system!

See THIS CALCULATOR at Reef Central ( one of the OTHER reef boards) for your math to calculate where you need to be in terms of overflow rates for your returns (and to determine pump flow rates). Total flow inside the display will be determined by the number of recirculating systems you employ to create total reef flow within the main tank, so although the returns from the sump do aid in total system flow, the total is not based on just the return flow rates from the sump. Most systems plan on turning over somewere between 8 and 10 times the total display volume from the sump each hour via return pumps, a good rule of thumb to met your MINIMUM needs for many mixed systems (certainly not a reeftop biotope...

).

Remember to build your system's biotopic conditions (lighting, current, nutrient levels, co-inhabitants, etc.) around the needs of what you consider to be your most important or most desirable single specimen, This will prevent the development of compromised conditions or conflicts that may harm some individuals when adding them to your system. The key is to think "total system" rather than just watever youthink would look good in the tank.

Welcome back to the hobby, hope this helps.

jamessp01 · 12-30-2007, 11:27 AM

Thanks for the info Wyatt. I took a look at the calculator and indeed, if I need to turn over 8-10x total display volume through the sump it looks like im going to have to get the tank drilled again before i use it.

One question on that though, do people tend to use the entire tank volume for this calculation or the volume adjusted for the addition of live rock etc... (i.e. the 120 will have an effective water volume of less than 100 gallons after the adddition of rock/sand and probably wont be full to the point that surface tension is holding in the last gallon.

A question on the actual 8-10x turnover rate as well, if the skimmer im useing in the sump is rated for 317gph and the chiller is rated for say 400gph, is there any reason i need 1000gph through the sump? I could see gas exchange being better, but is there some reason for it other than to support the peripherals in the sump?

kwjones · 12-30-2007, 11:35 AM

I would try to match your sump flow closer to the skimmer rating.

How big is your display tank and how big is your sump?

jamessp01 · 12-30-2007, 11:43 AM

Quote:

Originally Posted by kwjones

I would try to match your sump flow closer to the skimmer rating.

How big is your display tank and how big is your sump?

display tank is 120gal (48x24x24)

I have not built the sump yet, its going in the basement so it can be as big as I like. I was thinking somewhere in the 20 gallon range, larger if i build the refugium into it instead of seperate.

The only actual part of this setup I actually have is the RO/DI unit. I ordered the tank yesterday.

hng · 12-30-2007, 12:03 PM

I think people are moving away from the giant sump return pumps to provide flow in the display. This is good for multiple reasons. A smaller return pump means less energy used, less heat transfer, less noise, and less expensive start up cost. There are so many highly efficient, wide flow, compact powerheads (Tunze, Koralia, Maxiflow) available now that it really makes more sense to rely on them to provide the bulk of flow in a display tank. Wide flow patterns are very difficult to produce using a return pump unless you do something like a penductor, but then you need an even bigger and more powerful pump to make it work. A CLS is another excellent option, but for those of us not comfortable drilling a tank, the powerheads offer a great alternative.