Sump for a 20G tank & preventing flooding

[magma]

Hi people,
I'm new to this site and the aquarium hobby. I have a 20G high tank that I've just started, and I want to eventually keep soft coral. So the idea of a sump came up.

I think I want to have an overflow box connected to a Durso standpipe that drains down to a sump in my stand. I've done some research on making those equipment.

I'm concerned about the possibility of flooding. What can be done so that flooding will not occur when a sump is installed?

Also, what volumn should the sump ideally have for a 20G main tank? The space is my stand is not very big.

Thanks everyone

[Geoff]

if flooding is your main concern then i can not stress enough that you should drill the tank. when you drill the tank you are relying on gravity for the draining the tank. siphons fail. CPR has a special air pump that pulls air out of thier siphon tubes. this may be an option, but i have not used or heard about how well they work.

as for sump size, as big as will fit in the stand. a 5g should be plenty, but a 10g would be better. the important thing is to get the sump big enough to hold the equipment you want to put in it. the biggest being the skimmer.

G~

[Osurac]

I don't claim to know everything about aquariums, but I think I can hepl a bit here.

I have done something like what magma wants to do with 29 Gallon tank. I used an overflow that hangs on the back of the tank. It is basicly a small plastic box inside the tank with grooves cut into it, this allows water at the top to flow into it. Inside this box is an unverted U shaped tube, leading to another box outside the tank, which has half of its area blocked off to keep all the water from draining out of the U tube. This creates a siphon that can only siphon the water at the top of the tank above the slits in the box in the tank. In the second half of the external box, there is a hole drained in the bottom. Mine had a small pre filter attached. anyway this drain brings the siphoned water through a hose to your sump.

If you use this kind of hang on overflow, there is only one other way your tank can get drained, that is through your pump putting the water back in the tank from the sump. All you have to do is make sure the inflow from the pump is not too deep in the tank, and that will limit how much water can be siphoned back when the pump is off.

I recommend setting all this up, and then turning your pump off. Watch the water drain back into your sump, and be sure it will not overflow the sump before the water level reaches the inflow. If it does, turn the pump back on, raise the inflow, and test it again.

I'm sure this hang on overflow could be made, but I bought mine at a good fish store for $30.

Sorry if this is too wordy, or if you already knew all this, but I don't assume things are known, otherwise half the time, the info won't be understood.

[Geoff]

great explaination!

the problems come when the siphon fails, not when the power goes out, though this is another cause of flooding. what happens is the return pump keeps pumping water back into the tank yet none is siphoning back out. the result is an empty sump and the tank overflowing onto the floor!!! this generally a much bigger mess than the power outage situation. since we generally run our tanks with the water level as high as possible, this means an even greater chance for more water overflowing if a siphon fails.

G~

[Osurac]

Ahh hahh!! I have never had that happen, but I can see the danger. I think you have to be sure there is not too much turbulence in the overflow sending air bubbles into the siphon. Mine worked great for about 6 months (It never failed, I just got a bigger tank with a drilled bottom). I did have a small bubble in there, and watched it carefully, but it never grew or shrank.

I'm thinking the bubbles are why my siphon had the ribs in it, it seemed to make the bubble break up into little bubbles and move them out of the siphon. I also think the flow rate should play a factor here, if the flow is fast enough in the siphon it would carry small bubbles out, too fast & it won't carry enough water out, too slow & the bubbles will build up till the siphon breaks.

Hmm, it's more complicated than I thought, I must have gotten lucky!!

[volitansman]

I have been using the CPR overflow for quite a while now and it works great, I've purposfully let air into the overflow several times to test it and it sucks the air out and begins flowing as it should fairly quidkly. The only precaution you must take is to make sure you keep the pump free of calcium deposits so that if always restarts.

[Geoff]

flow has a lot to do with it. there is a fine line with siphon pipe size and return pump size. if the pipes are to big then you are right the bubbles can start to build up in the siphon and break it. if the siphon pipe is to small then the pump could outrun the overflow then you will also get flooding.

G~

[magma]

thanks for all the great advice guys.