Small tank flow question UNS 40A, MP10 + ???

[BitR0t]

Hey all, new reefer here. I have a UNS 40A, which is 40cm cubed or 15.75" cubed, right under 17 gallons total, 3 or so being in the back. The tank has an ecotech MP10, and the stock UNS sigma 15 return pump which is 238 GPH.

my sump, especially the third chamber with the pump, is fluctuating between full and sometimes pulling air. I am not sure if I have some variable restriction in the back, but my bet is the pump is not consistent.

I am considering replacing this with something like an Axis 20 or 40, to help create random flows with the MP10. Right now the MP10 is set to a max of 35 because it feels like I am just creating a tornado in the tank above that.

Any thoughts on using an Axis or something similar to assist with creating random flows? I also just want something a little more powerful than the stock pump.

 

[UNS_Brandon]

Is there any pattern to the pump chamber fluctuations? Do you have an ATO?

 

[BitR0t]

Is there any pattern to the pump chamber fluctuations? Do you have an ATO?

Hmm, I haven’t paid attention to patterns, I will try to keep closer check. I just notice big swings in display depth and then I look in the back and see it either full in the third chamber or nearly empty, pump is running in both states, I can feel flow on the nozzle.

No ato currently.

I’ll go ahead and pull the pump just to check if there is debris.

 

[UNS_Brandon]

If you do not have an ATO, you're going to see your water level drop in the pump chamber due to evaporation.

If it gets to the point that you're drawing in air, then not much water is being returned to the display--I'm assuming that's when you see low water level in the display.