return pump size?

hi, i got a quick question that hopefully has a quick answer. I have a 300GPH overflow that came with all the tank stuff when it was given to me. This tank use to have a sump but the pump stopped on it and then was never replaced. I can't find anywhere on it where it says a make or model or ratings even so i need to know how big of a pump should i go and buy to run the system? The tank is a 55G with a 20G sump/fuge running a 300GPH overflow

 

300-350 gph return pump.. A mag 3 is rated for 350gph..

 

Welcome to 3reef!

Here's a handy calculator even tho Night-Rida gave you you're answer.
Head Loss

 

ok i thought that makes sense. but that would be the bare minimum i would want to run right? Would you forsee any problems with me using a mag 5 and tee off the return and dump the excess back to the pump chamber?

 

thanks reefmonkey! I did look at that calculator before but was unable to understand how to use it or how it works. I entered in all the info i could but dont see what it calculates??

 

I have a 55g with a 10g+ wet/dry and a overflow rated at 300gph.. I use a mag 3 = 350 gph. no problem.. but I also have 2 maxijet 600 moded with sureflow mods and they put out 1400gph each for more tank/water movement.

 

probly can do that.. might be able to use a bigger u-tube in the overflow box instead too. depends though..

 

get a mag 5 and dial it back with a valve, that is if you even need to after head loss.. I used a mag 9.5 on my 30 gal with 10 gal sump and dialed it way back..

 

+1
I'd go this route. You don't want to overpower your overflow for obvious reasons, unless you can mod it to give it a little more flow like someone else suggested (bigger U tube). That said, you wont have enough flow in there alone so you'd want to add a power head or two. Rule of thumb, you want at least 20x turnover of your water an hour... so for you, minimum of 1500 gph of flow. I just bought a couple of these pumps off of ebay and so far they seem ok. No clue how long they'll last but they were freaking $15 each so i can't complain...

2 1300GPH WAVE MAKER CORAL FISH PUMP AQUARIUM POWERHEAD - eBay (item 300409006039 end time Apr-19-10 08:04:50 PDT)

 

this is one area I'm not good at putting in to words. Here's a chart that will show the loss of gph at varying hieght but remember that tee's, pipe diameter, valves etc. all effect flow and head loss. Also this chart is for mag drive's only.
Danner Mag-Drive and Pondmaster Flow Chart