View Full Version : Sump and Overflow?

ice cream jones
01/26/2009, 04:51 PM
So I will be putting together my first sump in a few weeks. I have a few questions. I will most likely be getting a CPR overflow, and a mag pump. I have a 90 gallon tank. 60x18x18.

1. What size tank should I use? Is my extra 20gallon too small? Would a 55 be too big? There is a 50 for sale on craigslist right now for $40 that i may buy.

2. How fast should My water be? It will need to be pumped up about 4 to 5 feet. I was thinking of the mag 9.5 pump rated at 950gph, with the cpr overflow box rated at 800gph. Is this too much flow? Too little? Too big of a difference?

I will most likely create a few chambers. One will be for carbon, one for my HOB protein skimmer.

Any information would be great. Thank you.

01/26/2009, 05:09 PM
I would get the biggest sump you have room for. You will never run into a time when you say "gee - i wish my sump wouldn't hold so much water", but you may very well have that "oh crap - sure wish i woulda gone with that bigger sump" moment!!! (been there, done that - go large!!!)

01/26/2009, 05:47 PM
i agree, the bigger the sump the better

as far as flow, put a ball valve after the pump so you can adjust it to your liking depending on what you decide is gonna go in the sump

01/26/2009, 06:10 PM
no such thing as too big a sump, go as big as you can.

I hate overflow boxes(get it drilled) and cpr overlfows are the worst kind imo, get a u-tube style like this-


As far as your pump goes, remember that your flow through the sump shouldn't be more than your skimmer can pump. For example, if your skimmer pumps 200 gallons per hour, your return pump should be about 190gph. If you pump water back faster than the skimmer can clean your putting dirty water back into the tank. Use powerheads for flow in the tank, not your return. Slower flow through the sump also eliminates any micro bubble problems. HTH

Jason Donohoe
01/26/2009, 07:10 PM
I recently built a sump for my tank and had a lot of the same questions. Here is what I think FWIW:

A 20g will likely be too small but if you are putting it under the stand that may be the limiting factor. How you get it into the stand may also be an issue if the tank is up and running. You may have the floor space for a big tank but not be able to fit it in through the doors. I solved that problem by dividing mine into 2 tanks. One tank for the water coming in from the overflow, equipment and return pump and a second tank for the refugium. Consider ahead of time if you want a refugium (you do even if you don't know it) an ATO, calcium reactor, GFO reactor etc and leave room for them in your plan.

Your return pump will lose a lot of flow pumping it from the ground to the rim of your tank. Click the link to the chart on this site for details:


I think the recommended flow is 6 times your display tank per hour through the sump. One method of reducing the flow if it is too high is putting a T in your return line with a valve on the T'd line. You can then 'vent' some water back into the sump. I know people also recommend putting a ball valve on the return line and just dialing back the flow.

If you drill your tank do it. You will have sleepless nights wondering if your siphon failed otherwise. If that is not an option (as it wasn't for me) consider an overflow that does not require a pump to re-establish the siphon. Check out this site:


Lastly, consider an in sump skimmer if the funds permit or leave a space to add one later on. I have found media in a reactor far more effective than in a chamber in the sump. 2 Little Fishies PhosBan reactors work great for both carbon and GFO. They can hang on or be installed IN the sump if space is limited.

Good Luck.

01/27/2009, 09:15 AM
i agree with all above, go big and you will be done with it. i went from a 45g, to a 55 to a 75 gallon for my 170. as for water floe through the sump 10 times your display min. from what i have read

ice cream jones
01/27/2009, 10:11 AM
6x the display? 10x the display? No faster than your skimmer? I'm confused lol. Anyone have any idea how many gph the 800s pulls?

01/27/2009, 10:25 AM
With a 4' head, the 9.5 would be pushing @ 800 GPH...which really maxes the limits of a CS100. Once the foam gets detritus in it, the flow rate may start to slow down, giving you overflow issues from your display.

For the size tank you have listed, the turn over may be on the high side, it may depend on how effective your skimmer will be in the sump at the rate. There may be some recommendations on the skimmer for turnover rates in the sump.

I'd go with a higher CPR unit than what you have listed if this is the pump you're going with. You will also need to get an aqualifter if you plan to use this one. I can tell you that I had one of these on my old 90 (and still occasionally use it when setting the QT up as a frag tank) and I've had way more overflow's than I care to talk about. CPR’s look nice, but I’m not a fan of their performance :(

01/27/2009, 10:32 AM
<a href=showthread.php?s=&postid=14253979#post14253979 target=_blank>Originally posted</a> by ice cream jones
6x the display? 10x the display? No faster than your skimmer? I'm confused lol. Anyone have any idea how many gph the 800s pulls?
If you think about it, why have water flow faster than your skimmer can process? people just like to have a number, thats why you hear 5x, 7x,10x, in reality, every tank is going to be different.

ice cream jones
01/27/2009, 11:31 AM
So what other overflow box does everyone suggest? Also, my skimmer is only rated to up to a 135g aquarium, So i doubt it would be able to keep up with water flowing at 900gph. Would it be safe to go for a cs50, and a mag 5 pump? I will be officially going with a 29 gallon sump, and will have probably 30-40lbs of rock rubble inside. That way it would give my HOB skimmer enough time to skim. Does anyone see any flaws in this?

Also, can anyone tell me the difference in a sump,. and a refugium? I like the idea of doing both...

Also, how to the eshopps overflows compare to the cpr?

01/27/2009, 12:33 PM
A Lifereef (http://www.lifereef.com/siphon.html) overflow is a far better overflow than a CPR. Much more reliable design.

For a sump, whatever you can fit. Bigger is better. Keep the flow from the return reasonable. For a 90G tank, 300 - 450 GPH or so.

01/27/2009, 12:48 PM
+1 on the LifeReef overflow. The CPRs are VERY unreliable. As long as you have sufficient flow through the U-tube you should never have any issues with bubbles interrupting your siphon. The U-tube design is also self-starting because the tube ends are always submerged so the siphon will restart. Yes, the LifeReef costs a little more but it's well made and dependable. With the CPRs they recommend an AquaLifter pump to suck out the trapped air - that should be a red flag right there. You can also add the AquaSilencer if necessary (or just make your own) to control the overflow noise. Drilling is best (or reef ready) but it's not always an option so save yourself some headache and go with the LifeReef.