Retur pump shooting bubbles

Good afternoon, I've had this problem 2 days in a row and I can't figure out what's going on.

It's a JBJ 12 gallon cube with an InTank media basket and Cobalt 900 return pump. It's worked great for a long time and now is having issues.

The water flow can't seem to keep up with the pump, so it runs the return pump resevoir nearly dry causing it to pump lots of air too. What I can't figure out is why that's happening. Have the rules of gravity changed at my house?

It seems when I unplug the pump to stop the bubbles the chambers all fill up again to their normal heights. I'm not sure what to do or what to check.

 

How ever the water gets to that chamber is somehow being limited.

I'm not familar with your set up, forgive me as I'm not trying to be smart, but could it be a low total tank volume water level?

 

I thought about that and topped everything off as much as I could and still had the issue. The way the tank works is a 3 chamber system in the back. In the tank there's a plastic screen intake which goes to the first chamber. The water goes in at the top and drops to the bottom of chamber one where it then goes to chamber two from the bottom and flows up where it then goes into chamber 3 where the pump is, goes top to bottom and then through the pump out to the tank.

On the journey it goes through an InTank media basket which has filter floss, then chamber 2 has chaeto, then 3 has some ceramic bio media and the pump. It's been set up that way for at least 6 months with no issues until yesterday.

 

Is the floss, and chaeto free of excess detritus? That'd slow it down

 

Because of the way your tank is set up, your return chamber will be the only place you lose water volume through evaporation. When you stop the pump, it would be normal for it to fill until the water level in the main DT gets too low to overflow into the back. Unless you have something overflowing onto the floor (or the laws of gravity have indeed changed), that's the only possible way for the return chamber to get low enough for the pump to draw air.

 

The water would still have to go somewhere if there was enough in the system.

 

I'm thinking it's fixed because it hasn't started shooting bubbles as quick as before, but I'm still leery. I think what was happenening was there was some sort of blockage in flow from the first chamber to the third, but not a total blockage. There was just enough water getting in to keep the pump running, but the pump would pump faster than water could return. I'll keep watching it today and hopefully the problem doesn't return.

 

Isn't that how DT usually run over?