need help with custom refugium

[daveysmart]

I am not sure if I am posting this in the right forum or not but I could use some help with my behind the`tank style refugium. Basically it is a hob fuge that doesn't hob. I made it with acrylic, it is 11 inches long x 4 inches wide x 11 inches tall and sits on the stand behind my 3 gallon picotope. The pump is a RIO 800 about 200 gph, but probably a bit less since it is pulling the water instead of pushing it over the top. The exit overflow is 3/4" bulkhead with a slip strainer on the inside and two 90 degree elbows on the out. I got this running on Sunday, and it is working except for one problem. The outflow sucks air in, it makes a little whirlpool and sucks air and then shoots out bubbles into the display. Can I get rid of the bubbles by reducing the flow volume? So if I shave down the impeller a little bit will it stop the overflow from sucking in air and shooting bubbles into the tank? I am having trouble figuring this one out

I dont have any good pictures but here is the sketchup model I revised to reflect actual construction.

Thanks All!

 

[returnofsid]

Sounds like the area of the refugium, where the water exits, is not staying full enough. You might need to put a 90 inside the refugium, pointing down. This should ensure that that piping is always 100% under water and deep enough under water to not suck air from the surface. You might even need to put a short length of pipe between the 90 and the bulkhead to get it even deeper into the refugium.

 

[Pentagona]

elbow down on your return so that the return pipe doesn't want to venturi.

 

[daveysmart]

That makes perfect sense. Thanks for the quick answers!

 

[Chichas01]

Sweet diagrams! What did you use?

 

[braddo]

Sweet diagrams! What did you use?

looks like the drawings were done in Google Sketchup http://sketchup.google.com/

Its handy for designing 'fuges

 

[braddo]

Daveysmart, do you have any trouble getting the pump primed when the intake tube is filled with air? Originally I wanted my pump sucking from inside the refugium like that however I figured it probably wouldn’t work well without a way to prime the intake tube first so just stuck the pump in the display tank.

 

[daveysmart]

I wasnt sure about this either but I tried it anyway. I really didnt want that pump in the display tank. It primes but it takes a minute or so and makes alot of bubble which dont get through to the tank too bad. There is a siphon effect when the pump is turned off. I want to drill a hole just below the water line but I am not sure if it will be able to reprime itself with a hole there. Anyone know? I guess I could try it and fill it up with some glue if it doesnt work.

I added a elbow to the intake and it took care of the bubbles, however it made the siphon effect worse so I am going to try and add a overflow baffle ( not really sure what its called) around the bulkhead to see if that will keep the water level high around the outflow but not have alot of back siphon volume. I guess a picture will make it more clear. I will probably wait til the weekend to try it out. Thanks again guys.

Oh yeah, sketchup! Its free and fairly intuitive to learn. Its alot of fun to mess around with. I have been using it alot lately at work.

Edit: I updated my thread in the members showcase forum with a couple of pics of the new setup. (You can click on the signature below)