View Full Version : A pump that halts air return

05/13/2018, 05:21 PM
I'm frustrated at solving a problem that seems like it should be quite simple, but I'm having trouble with.

I have a 120 gallon marine aquarium. I'm 2 years into the hobby, so by marine standards, somewhat new still. My sump based system uses an overflow, sock receptacle, and after flowing past my skimmer ultimately gets pumped back up with a basic, AC, fixed rate return pump.

I am conscientious about cleaning and replacing my sump socks, but of course they don't dirty all at once, as it's a variable process. Over a few days, the input into my sump doesn't keep up with the output back up.

So, although I do have my water levels set so that no disasters happen, the pump will begin pumping air into the tank, as the water level in the sump decreases (in flow into the sump is less than the outflow). The amount of air pumped in is rather large, freaks the fish out who all go into hiding, and if I'm out of town for a couple of days, this is the state of the tank until I return.

I know that there are sophisticated and expensive solutions I could do with an Apex system and attached pump, float sensors, etc., but I was hoping for a DC pump that would detect when it's pumping air and decrease it's flow.

I did have this recommendation from Marine Depot, the Reef Octopus VarioS-8 pump. At $375 it's a bit of expensive, perhaps. But it comes with a float and control mechanism, and may solve the problem.

But .. wouldn't you think there'd be a simple float a person could buy that would attach to even an AC pump and simply switch it off when the water level in the sump is too high (or the water in the display tank is too high)?

I'm not a plumber or advanced with electronics, and I'm hoping for a packaged solution.

What have others done to solve this problem? It must not be that uncommon, or am I missing something obvious?


David R., from Carmel, Indiana

05/13/2018, 05:24 PM
Sorry, one typo that's kind of important, the sentence, "and simply switch it off when the water level in the sump is too high (or the water in the display tank is too high)" should read, ... " when the water level in the sump is too low (or the water in the display tank is too high)".

05/13/2018, 07:49 PM
I think a simple ato to keep the sump level consistent would be easier(and cheaper) than a new return pump with the feature of recognizing air intake.

05/13/2018, 08:23 PM
Could you maybe add a second line from your overflow (or a second overflow), set higher than the first, so that when the flow from the first backed up, the second would take over and deliver water to your sump (and no sock on this second one, so no water backup)?


05/13/2018, 10:28 PM
I think you need an auto top off, you could get a DC pump and some of them come with float switches that you can set to shut off when the water gets too low, I don't think you can set them to turn down the flow I think it's an all or nothing solution. But really it sounds like you're not making up for the water that evaporates, when you have a large display tank and relatively small sump, the water level in your display tank is set by how fast water gets pumped in vs how fast it flows out and reaches an equilibrium that only changes if one of those factors changes, so when water evaporates it doesn't change the water level in the display, also most of the sections in your sump are set to a constant water height because water has to flow over a wall to get to the next section so the only place the water level changes is the return section of your sump and because it's so small the water level can drop a few inches a day, the best way to manage this is within an auto topoff that adds fresh water as it evaporates

05/13/2018, 10:32 PM
Throw out the socks, problem solved

Sent from my iPad using Tapatalk

Kevin Guthrie
05/13/2018, 10:51 PM
You have a properly sized overflow in the tank, right? The socks are backing up the water from the tank to the point where the water level in the tank is rising, correct?

Your options are to clean the socks more often, add a valve to your return line to lessen the flow from the return pump, increase the number of socks, or add a tee before the socks thru which water can bypass the socks when they clog.

The most beneficial thing would be to clean out the socks daily or swap in clean ones daily.

05/14/2018, 04:01 AM
I'm a little confused.....

Only if your pump is over rated for your drains should this ever become a problem, Or if you do not have an ATO.

If it's the first, the easiest solution would be to put a gate or ball valve on the return pump and just create some false head. In essence tuning the pump to match your full siphon line.

If the latter, then either get an ATO(tunze makes an awesome one thats been tried, trued, and tested for years), or buy a DC pump that recognizes low water situations and shuts the pump off. Not ideal, but it would save the pump from over heating and burning up spewing caustic material into your water.

While socks can certainly clog up and create an issue, it's usually not enough that it would cause your return section to loose enough water for the pump to suck air. You either do not have enough water in your sump to overcome it, or you lack a properly functioning ATO.

When I did run socks, if I forgot to change them out they simply just overflowed back into the sump. Never had an issue with them filling up and creating low water situation in my return section of the sump.

05/14/2018, 04:19 AM
Do you have a picture of your sump, is it diy or name brand? Either your return section is really small or your sock area isn't allowing the backed up water to overflow out soon enough.

05/14/2018, 05:46 AM
If you really want to keep the filter socks I would recommend changing to a coarser mesh.
There are other solutions too.. Increase water level in sump slightly to prevent this..
Create a lower bypass to allow the socks to not effect the water level so much..
and more..
Its really not a problem that should be addressed by doing anything other than focusing your attention right at the socks.. They are causing this problem.. Fix that..