I have a 200 gallon tank. It has 3 holes drilled in the bottom and presently the water is pumped up through 2 holes in the bottm and out a series of vents about 3- 4 inches from the bottom of the tank just above the gravel. The water from the surface of the tank spills into a column in the middle and through the third hole back into a 30 gallon tank underneath that holds the filter media.

When we set this up we put a check valve between the pump and the 2 holes that the water enters the tank. It has been set up for about 3 years now. I found out when we hasd a power faliure that the check valve isn't closing.

The water slowly backs down into the 30 gallon tank and overflows.

I'm guessing that the check valve is just clogged with the gunk that tends to stick to the walls of filters and tubes just enough to stop it from closing completely. It is glued inline PVC pipes so it would be difficult to clean. We put a valve on one side of the pipe going into the tank to adjust the flow and keep it even but the farther side has no valve so I can't stop the water flowing back to work on the plumbing. A stupid mistake.

I am planning on breaking down the tank and redoing the system so that if the power goes out and I am not home or awake to grab the pump out of the filter and set it up near the top of the water, that the entire tank will not empty.

What would be the best way to do this without relying on a check valve?

One way I have been thinking of is to bring the water in a pipe tat goes up to just under the surface inside the tank with an elbow bringing it back to the bottom of the tank. I could put a couple small holes in the elbow at the top to break the syphon so the water level would drop only a couple inches. I don't want the water to go in at the top and out at the top also because there would be so little current through the tank.

The problem with this idea is it would be so ugly to have all this extra pipe inside the tank to try and hide.

Another thought would be to reverse the waterflow so that the water enteres the tank from the center column and chang it to a aquatrerarium so the tank is only 12-13 full of water, the return water goes into pipes several inches from the bottom so the return is just under the surface of the water. This would sove my problem of having small fish flowing into the filter.I have a screen on it but they get in anyway.

Can anyone think of any other ideas I can consider before redoing this?

The tank is presently stocked with:

3 white mollies

5 rummy nose tetras

5 black skirt tetras

3 white clouds

1 old yoyo loach

2 bumblebee catfish

trumpet snails

Half of the bottom is covered with crypts about 3 to 8" tall.