powerhead blowing air bubbles into tank?

I have been setting up a JBJ 28g for my son that came with only the tank, no pumps, no media basket, no cover etc. It is all set up with 2 mj 750's in the back of the tank that feed the returns. They are old left over pumps I had and I noticed today that one of them randomly shoots out bursts of tiny micro bubbles. Any ideas what can cause this?

 

Sounds as though you need to raise the level of the water in the tank.

Use only FW (RO/DI) if possible.

I have this tank and it can capture bubbles and release them, if it becomes more problematic a simple top off with FW will help.

You might want to check the specific gravity as well.

 

Air in the pump or air is getting in where the pump is at and it is sucking it up. Increase the water level in the back so bubbles can't form in the return section and get caught by the pump.

 

Or lower the powerhead until you can get some RO/DI water for a top off.

 

The pumps are actually submerged in the back of the nano cube. They are about 20 inches below the water. One is blowing bubbles and the other is not

 

Try cleaning the one blowing bubbles thoroughly.

 

I quickly did that, but I'll try some vinegar and see if that helps

 

I've had this problem before with my Taam Rio pump. Use a turkey baster on the pumps. Don't try to fill it with water, but squirt the pump (intake area) with air while in the tank. This should free any blockage that might exist within the pump and air bubbles will cease within about 30 seconds or so.

 

The air bubbles you are seeing are from cavitation. There is not enough water flow going past the impeller.

 

I think you are right 2in10. The power heads suck the water down into the back chamber and I noticed that in is creating a waterfall effect into that chamber. The problem is that the tank is pretty full. I am wondering if maybe the power heads are too powerful. I will try to add a bit more water to see if it helps