Internal Overflow Help

[KaZoN]

Hi All

I need some advice on the design of an internal overflow system for a new reef tank that I am getting custom built

The tank itself is 60"x18"x28" which works out at approx 130 Gallons

I want to push through about 900GPH (any comments on this please feel free)

According to the overflow calculator on reef central that would require an outlet of 1.25" and a linear overflow of 14 inches.

I am thinking about putting in a central overflow system with 1 drilled outlet and 2 drilled returns. (All drill holes will be on the bottom of the tank)

I would greatly appreciate some advice on the best way to have the overflow box constructed including the size of the outlet and return holes. This is holding up tank build as I'm not entirely what to tell the manufacturer as this is my first marine build

Many Thanks in Advance

 

[loganj]

I don't have any flow charts to show you but I'm working on a 180g RR tank now. It's a Glasscages tank with two internal overflows. Each overflow has a 1.25" drain and a 1" return. I built Durso standpipes out of 1.25" PVC. Make sure your overflow is large enough to accomodate a Durso standpipe. Mine just barely fit due to the return line coming up beside it. This system handles 1800gph with no problem. It would flow more than that I'm sure. Based on that, I think you're good with one 1.25" drain as long as you don't intend to up the flow through your sump later. 900gph in a 130 gal tank isn't alot of flow if this is intended to be a reef tank. However, you can always add a closed loop pump to up the flow if your sump is maxed out. If you have too much flow through the sump, you will have problems with microbubbles...closed loops don't have that problem. I would shoot for 2300-2600 gph total flow if it's a reef or even a FOWLR. JMHO.

 

[KaZoN]

Would the method I have describe in my first post provide enough circulation without the need for adding powerheads to the tank?

How does a closed system work? Any links with images would be greatly appreciated

Thanks

 

[JM]

I run about 1500gph through the returns on my 120 and its a FOWLR i would recommend at least 2000gph for a reef 2400gph being optimal. Just look at the AGA overflow system and base your tank off of that. Two 1" drains and two 3/4" returns or you can make your returns 1" also.

 

[KaZoN]

Thanks for the reply

Using the AGA design I assume that the overflows would be in each corner of the tank as opposed to a central overflow?

What size would the corner overflows need to be?

I was hoping to use a central overflow as one end panel of the tank will be visible in the room.

 

[melosu58]

Moved to Hardware and equipment discussion

 

[loganj]

You can put the overflow anywhere you want it and it'll work fine. I'd go with a 1.25" drain and a couple of .75" returns. You could go with two 1" drains, but I think the 1.25" will handle it just fine. I would use the Durso standpipe because it works and it's quiet. A closed loop system is where the pump draws directly from the aquarium and pumps the water right back up to the aquarium. All it's doing is creating currents in the tank. I'd use a big strainer on the pump intake so inverts don't get sucked in...it usually kills them.

 

[KaZoN]

OK I'll stick with the original central overflow design with one 1.25" drain and two .75" returns.

I am planning in putting about 90lbs of live rock and a 4" sand bed to cater for the filtration.

I will be using the 1.25" drain to feed a sump where I will have a skimmer, heaters, refugium etc and returned to the tank via an aqua medic pump. Most likely an Ocean Runner 6500.

Will this setup alone cause enough turbulence in the tank so I don't need any additional equipment like powerheads in the tank itself?

Thanks

 

[loganj]

I would go with an external pump if possible. They are quieter, last longer, and transfer less heat to the water. 900 gph is not enough flow for a 130 gal reef tank. It's enough going through the sump I think, but you need more flow in the main tank. I would go with a closed loop pump system using a SQWD or at least multiple returns. Powerheads clutter the tank, require cleaning, add heat to the water, and usually don't last nearly as long as a good external pump. You really should have at least another 1200-1500 gph flow in this tank. Examples of pumps you could use are an Iwaki 30 RLXT for the sump return and an Iwaki 40 RLXT for a closed loop. Remember that the pump isn't going to pump what it's rated. Most pumps are rated at 0' (some are rated at 4') head. By the time you pump the water up to the tank and figure the frictional losses from elbows and such, your pump output will be decreased somewhat. If you slightly oversize the pump, you can always choke it back some with a valve on the PRESSURE side...never on the suction side.

 

[KaZoN]

Hi Sorry for all the questions but I'm very new to this hobby.

Am I right in assuming that I need a closed loop in addition to the sump?

If so I also assume that I need extra drill holes in the tank? Are these in the bottom or the back of the tank or both?

Anywhere I can read about closed loop systems and their design as I am struggling to understand how they work and how to set these systems up.

Thanks

 

[loganj]

IMO...yes, you need more circulation and a closed loop pump system would probably be the best way to get it. You don't have to drill any extra holes in the tank although it'd be nice to have holes in the back glass for the intake and returns of a closed loop pump. Here is a link to a picture of a closed loop system all put together but not in the aquarium. http://www.melevsreef.com/plumbing/closedloop.jpg
Your suction line comes from the main tank to the intake of the pump...water is pumped back up to the tank through the returns. It does the same thing as powerheads would in the tank...but the only thing actually in the tank is some plumbing that is easliy hidden.

 

[KaZoN]

Thanks for the pic.

I assume that this hangs on the back off the tank so to speak.

Could I add an additional internal overflow as the inlet to the closed loop system feeding back into the back of the tank via drilled holes.

If this is correct how may return holes would you sugggest I use for a 130 gallon tank to achieve a decent flow.

Thanks

 

[loganj]

You could add an internal overflow to feed the closed loop, but I wouldn't for two reasons. One, most of the DOC's in the tank will be at the surface and you don't want to skim this layer of water and churn it all back up through a pump...you want that going through your sump where there is a chance some of it can be removed. Second, if your sump return pump quits for some reason, the water level in the tank is going to drop as the tank drains into the sump. If you are running the closed loop from an overflow, it will run dry in this situation and likely ruin the pump. I would either come over the top edge with the suction line or drill the back of the tank and use a bulkhead fitting with a large strainer. The reason to use a large strainer is so snails, cucumbers, anemones, ect... won't be sucked in and killed. I would split the return into at least two outlets. You really want one return blowing just under the surface of the water. This will create lots of surface turbulence and increase gas exchange. It also helps cool the tank by increasing evaporation. You can use your sump return for this...be sure to drill a siphon break in that line so the water won't siphon back through the pump in the event of a pump/power failure. If you were to use a larger pressure rated pump, you could have three outlets with two of them coming off a SQWD. The third would be valved so you could control the pressure and flow through the SQWD. This would give you more than enough flow through the tank as well as some alternating flow that would simulate wave action somewhat. The target in a reef tank is turbulence. No coral is going to do well with a pump outlet blasting it 24/7. You want changing, colliding, turbulent currents that simulate the waves crashing over the reef as closely as possible. The 180 I'm installing will have one pump (1150 gph) going into a 1" Sea Swirl which will rotate back and forth 90*. The other identical pump will go through a SQWD with outlets on opposite ends of the tank. There will be at least one 5 gal surge device and possibly two. I guess I'm writing a book here...sorry. I get carried away sometimes. But you get the idea about the currents you need to create.

 

[KaZoN]

I really appreciate all the great advice that I am getting.

Dont worry about writing too much I need to do all the reading I can at the minute

I'm going to do some drawings tomorrow and post them up for you to have a look. If you dont mind you can tell me what you think of them and what corrections I should make.

Many Thanks

 

[KaZoN]

Ok, I finally got round to getting the drawings done.

I'd really appreciate any feedback on my proposed system

Thanks

 

[loganj]

I think that will be fine. I assume you are going to use 3/4" bulkhead fittings for the closed loop? Be sure when you have the tank drilled that you have the holes sized for the bulkheads you want to use. A 1" bulkhead takes like a 1 7/8" hole...or something about that size...I can't remember the exact sizes. I'd order my bulkheads and then have the tank drilled to fit them. Your drawing looks fine to me. If you are going to run one pump on the closed loop, I'd have 1" lines going to and coming from the pump. Then you can tee down to 3/4" when you split the line to go to the tank. Make sure you put valves on both lines so you can remove the pump if you need to. I would probably put valves in the pressure line after the tee as well so you can adjust flow. Lastly, I would either put unions in the line or, my preference, use true union valves. That way you can break the plumbing down easily. If you use unions, be sure you put them on the pump side of the shut off valves or you won't be able to remove the pump without a mess. HTH.