Plumbing a 72 gallon Display Tank and 29 gallon Refugium at the same tank height

[dgmanny]

I am really enjoying this forum. I recently installed a 72 gallon bow front and the design of the stand makes it impossible to put a decent size sump/refugium in the stand. However, I have the ability to install a 29 gallon tank at the same height (not lower or higher) as the main tank in a room right behind the 72 gallon tank. I just need to run the plumbing through a small opening in the wall. Neither tank is drilled. I have a few questions that I would really appreciate any answers.

First, what is the best way to plumb between the two tanks? Can I just install a pump from the 72 gal tank to the 29 gal tank and install a siphon return between the two tanks? Or do I need an overflow box in the main tank? How deep should I make the siphon outlets in each of the tanks? What flow rate pump would you recommend and what diameter pipe for the siphon? Should I put the pump in the 72 gallon tank or in the 29gallon tank? It seems to me that the main problem that could arise is if the siphon breaks and the pump overflows the other tank. What fail safe could be built in to avoid this? Thanks so much.

[thegrun]

I would put the pump in the 29 gallon refugium so you do not need to look at an ugly pump in the main display tank. Yes you will need an overflow box of some type in the DT to keep fish from being sucked into the refugium. I would look to pump around 500-700 GPH through the refugium. There is going to be a very fine line between functionality and disaster in this set-up. Float switches in both tanks to shut down the pump if the water level rises too high would be a must in my mind. I would set the 29 gallon tank lower than the DT if I was you and use a more conventional sump approach to the plumbing and not fill the sump tank to the top if possible.

[floydie83]

Do you already have the 72g setup and filled with water? I have a 29 gallon sump as well but I was able to fit it underneath.

You are right, it will not fit with through the front or back opening. With the tank off you can remove the top center brace temporarily and place the 29 gallon in the stand though the top. Then replace the brace.

Actually after reinstalling the brace I felt better because I was using several screws instead of the large staples that held it there before.

Let me know if you have more questions. I can post some pictures tonight if you need.

[dgmanny]

Thanks for the quick replies. I already set up the display tank and didn't consider that a sump wouldn't fit below. Live and learn.

It also sounds like a same level tank is a bit risky. I definitely need to avoid a flood. I will try to figure out some alternative locations at floor level, maybe in the basement. Thanks again.

[floydie83]

the basement will require a pretty hefty pump to get the water back upstairs. Good luck with it all.

[Fizz71]

What about a mock-sump in the stand that feeds both tanks? I know you said there isn't enough room for a decent setup, but if you just put ANYTHING in there as tall as you can make it with 2 submersibles (one to each tank) and run the water level low. Keep enough room leftover to handle overflow water, but only run a shallow sump so if the power goes out the water just winds up in the sump.

Your biggest challenge will be overflow failure--you'll have to run the water levels low enough that if one overflow fails, there is enough room in the tank to handle the extra water since it will ALL wind up in 1 tank. Top-off will not be ATO either..too dangerous.

Personally I'd look for another solution, but then again I've been burned by so many "overflow" setups that I won't run anything that isn't drilled anymore so I'm biased.

[FearTheTerps]

Honestly I don't really see a problem with this set up, as along as the water levels of both tanks aren't exactly the same. A 72 bow is 30 inches tall, and a 29 is about 16 inches maybe(not 100% sure) but even in the sump your water level for most skimmers is about 8-10 inches. That would make the sump 20 inches lower the the DT. As long as all the normal safeguards are in place how is this any different then a sump that sits on the floor. Maybe I am missing something in my logic, but it actually seems to be better, you won't have as much head loss for your pump, and with less plumbing you won't get as much water draining back into the sump in the case of a power failure.

[trb]

I have to agree with Fear. Are the bottoms of the tanks at the same height? If so, your overflow box will drain into the 29 gallon tank, (which is about 18" tall) and then your return pump will pump the water back to the main tank just fine.

[dgmanny]

I should have posted a drawing because it is confusing, however i appreciate the input. The height of the 29 gallon tank is only once inch lower than the 72 gallon tank because the height of the cabinet the 29 gallon sits on is higher than the 72 gallon stand. I may just buy an overflow and test it using a low water level in the tank (i also have a 20 gallon long I may try). If it doesn't work, i will have to modify a built-in cabinet to put the tank at a lower level, which i was trying to avoid.

Or I may bite the bullet and drain the tank (i've only had it up for a month and only have live rock and a couple of fish), drill the back to add an overflow, and put in a sump in the stand while I have the tank off of it. Thanks again.

[trb]

OK, 1" drop won't work unless you had the tanks practically back to back and had the external overflow box in the other tank, with a long "U" tube between the tanks. But that could be troublesome to keep a flow going. The 20 long might work better, as it is 6" shorter than the 29, giving you a drop of about 7" from the top of the 72. To keep the flow into the sump going on gravity alone, you should have the outlet hose height going into the sump lower than the water level in the external part of the overflow box. If you can do that, it should drain just fine.

[dgmanny]

I will give that a try. Thanks.