Sump Pump.

[Allen]

Just been researching the sump idea for my 30G tank - soon to be saltwater.

Could I use my fluval 304 canister filter to pump the water from the sump back to the main tank ?

I realise I need to remove the filter media and fill it with live rock rubble or something.

This pump shifts a fair bit of water and I didnt really want it going to waste and not be used in my system.

I just now need to figure out how to get the water from the tank to the sump - its not a drilled tank, so I will need some sort of over the top action or get the tank drilled.

Your thoughts please...

Thanks.

 

[andywg]

I wouldn't use the fluval cannister. Fluvals are getting a rep for leaking. I know of at least 3 people on this forum who have suffered leaking Fluvals in the last year (myself included). Also, it will not be very good for moving the water back, far better to use a dedicated pump that is designed to deal with the head pressure.

I always recommend drilling. You can get drill bits from Hong Kong for about US$8-$12 including delivery. Drilling is very easy so long as you don't have tempered glass. Very few tanks have tempered glass on the sides so you are almost always safe on that if you are unsure of the bottom.

Drilling is a little bit safer than overflow weirs as there is no risk of loss of suction. It is probably a fairly small risk that the overflow would lose suction, but the consequences of if it did worry me far too much to ever use one instead of drilling. Especially as I now know how easy it is to drill.

 

[SkiFletch]

Agree totally, drilling (at least on the overflow side) is the way to go . If you're worried about your handiwork capabilities, ask around at your LFS cause they probably know somebody who sets up tanks and would do it for a small fee ~$20-$25.

I also agree that you'll want to use a dedicated pump for your return instead of a cannister. Cannisters are not designed to push water up, just re-circulate it. I'd look into a submersible pump with threads on its outlet for ease of construction. Something along the lines of a mag 3 or 5 for a 30g tank would probably be suitable.

 

[Allen]

Canisters not designed to push water up ?

This one has sat under this tank for 18 months pushing water up.

Now I am confused.

 

[SkiFletch]

Physics is a pain isnt it

Your canister tank is a sealed, level system. Once water goes over the rim of your tank, it siphons all the way down into the canister and then all the way back up to the water level of the tank. Remember, water seeks its own lowest level once a siphon is started and the water from your tank will want to fill both supply and return tubes to the canister once siphon is started. So the pump in the canister filter has to do very little work because gravity pushes water both down and up in the sealed top system.

Now when you take the top off of the canister filter (basically creating a sump), everything changes. First you have to get water down to the sump via an overflow. But because the sump has an open top, gravity will prevent water from going up the return hose. So you now have all this water under the tank that needs to be actually pushed back up with no siphon action to assist. This requires a pump actually capable of pushing water up 3-5 feet which is much different than the 3-5" that the closed top canister has to deal with.

Its a really tough physics concept to understand and I hoped I explained it. If you still dont get it, lemme know and I'll try again with pictures

 

[Allen]

Now I get it !