Closed Circulation Loop Input (Front)

In my never ending quest to squeeze more water movement into my tank I originally tried to use dual return pumps (Iwaki MD70RLT and MAK4) from my sump to the display tank. I ran the tank this way for several months. However, I had to cut back the flow a bit as the teeth spacing on the overflow chamber were not wide enough to handle such volume. I even removed a few of the teeth to increase the amount of water that can enter into the overflow. In the end I had to turn off the second pump.

I was inspired to try a closed circulation loop after a visit to Sanjay Joshi at Penn State University to see his amazing 500 gallon reef tank that had 4 closed circulation loops.

Typically closed circulation loops require the tank to be drilled to allow for an input in the lower back panel. Being that my tank was already established I had to find another method. I think I came up with a pretty clever way of doing it. I converted my return lines from the sump to inputs for a closed loop.

Closed Circulation Loop Input (back)

The first step was to free up the tank return lines from the sump. This was pretty easy to do. I decided to use two ¾ inch Sea Swirls which was a wonderful addition to the tank in generating random current patterns. Once the return lines were not used, I removed the lock-line piping and elbow (was drilled with anti-siphon hole). I then constructed the picture you see above. It is a ¾ inch elbow on the pipe on the inside, a short piece of ¾ inch PVC pipe to get to the other side of the overflow chamber, ¾ inch street-ell pointing downwards, ¾ inch female adapter and finally a ¾ inch suction strainer. I built two of these, one for each side.

Under the tank, the old return lines now being used for the closed circulation loop were replaced. I have ¾ inch insert adapters screwed directly into the bulkheads. I then used ¾ inch clear flex tubing (which I wrapped in black electrical tape to prevent algae growth inside the tubing. Both lines joins together just before the pump.

Closed Circulation Loop Output

To construction this junction I started with a standard 1 inch Tee. I have ¾ inch threaded reducer bushings in two sides of the Tee. In the reducer bushings I used ¾ inch insert adapters where the flex tubing is connected. This allows the two inputs to join and step the pipe size up to help reduce any restrictions on the input side of the pump. The opening of the Tee goes to a 1 inch ball valve, then to a 1 inch union. The union is connected to an elbow with a 1 inch to ¾ inch threaded reducer which screws directly to the input side of the pump.

The output side of the pump is a ¾ inch to 1 inch threaded reducer bushing that goes to a 1 Inch Union, to a 1 inch ball valve, to a 1 inch female adapter with a 1 inch insert adapter screwed in. I then use flex tubing (again wrapped with black electrical tape to prevent algae from growing in it) up to the top of the tank where the output manifold is.

Closed Circulation Loop Output

An insert adapter is screwed into a female adapter which is connected to a 90 degree elbow. The 90 degree elbow points towards the front of the tank. The 90 then connects to a 1 inch ball valve (not pictured) and then to a Union (not pictured). These were added after this picture was taken to make it easier to remove the top part of the closed loop (manifold) when I needed to perform tank maintenance. After the Union is the Tee (Pictured) which then goes to the left and right side of the tank. Finally each side has 1 inch female adapters with 1 inch to ¾ inch threaded reducer bushings. The old lock-line returns then screw in. The lock-line pipe is the black flexible pipe in the picture, this works great for fine tuning where the output nozzles are to be placed.

Just remember to add water to the line before hooking up the flex tubing to the manifold on top of the tank. This is needed to prime the pump.