Potential return pump issue

Jasongtr · Mar 6, 2023

My fish only tank has been running for about 3 weeks with brand new plumbing and a brand new tmc reef 4000 return pump that was set to power number 6 and the gate valve tuned accordingly.

Last friday i noticed the water level in the weir dropped a couple of inches so turned the pump up to 7, yesterday that became 8 and today 9 wasnt quite enough and 10 just a touch too much.

The tank is a DD 900 reef pro and for those that dont know they have a fairly small return plumbing at just 20mm, ive taken the pump out and cleaned it and that made no difference but i doubted it would as the pump and tank are so new, ive even changed the pump for an identical one as i bought two at the time, nothing changed so im at a loss as to what the issue could be.

Only other thought is the return plumbing has got very dirty and causing a bit more of a flow restriction, i can of course take it all out and check and clean but something just occurred to me that might well be normal ( forgive me as this is my first tank with a sump) ....

My thought is there could be an initial build up inside the pipes that would need the systems return pump/gate valve to be adjusted in the first few weeks or months as the pipework gets a layer of gunk in it, ive no problem running out and buying a more expensive pump but the two ive got and tested are doing the same thing so it seems unlikely both are dying when one has literally been in the sump for 30 minutes

Any ideas??

o2manyfish · Mar 6, 2023

As biofilm and gunk builds up on the plumbing it not only slight restricts the flow but more so slows the flow of water across the surface of the plumbing. So the water can't travel as quickly. Most modern aquarium pumps are volume flow pumps not pressure pumps. They are designed to move water but not force water thru the plumbing. The more resistance within the plumbing the slower the water moves the less volume goes through it.

You've already tested and proved it's not a pump issue by swapping out pumps. This is just the process of nature - as biology develops within your aquarium.

I don't know if you have any experience with boats - But this is why boats are lifted out of the water or have bottom paint applied to kill stuff from growing on the bottom of the boat - because all that 'life' slows the water flow across the bottoms of the boat - slowing the boat.

Dave B

Jasongtr · Mar 6, 2023

o2manyfish said:
As biofilm and gunk builds up on the plumbing it not only slight restricts the flow but more so slows the flow of water across the surface of the plumbing. So the water can't travel as quickly. Most modern aquarium pumps are volume flow pumps not pressure pumps. They are designed to move water but not force water thru the plumbing. The more resistance within the plumbing the slower the water moves the less volume goes through it.

You've already tested and proved it's not a pump issue by swapping out pumps. This is just the process of nature - as biology develops within your aquarium.

I don't know if you have any experience with boats - But this is why boats are lifted out of the water or have bottom paint applied to kill stuff from growing on the bottom of the boat - because all that 'life' slows the water flow across the bottoms of the boat - slowing the boat.

Dave B

Thanks, i was initially worried my new pump was failing already then thought after ruling that out its got to be an added restriction in the plumbing, either a unnatural clog or a natural build up

Thank you