How to set up a protein skimmer

There are lots of protein skimmers available for marine tanks, and they have many benefits including increasing oxygen levels and reducing nutrients. But which one is right for your tank, and how do you set one up?

There are several types of protein skimmer: Internal, hang-on, and sump based, with sump based skimmers sub-dividing again into internal (which sit inside the sump,) and external, which sit outside. The best overall package skimmers are those which sit inside a sump, as they combine performance with the reassurance that if they overflow, they do so into the sump and won’t risk a flood. But skimmer guardians are now available which can cut power to the skimmer in the event that the cup is going to overflow. 

Place the skimmer into the water, plug it in, and it will start to make bubbles. But’s it’s the height of those bubbles within the skimmer chamber that is critical to setting up a protein skimmer. With internal skimmers (that go inside the main display tank,) the neck and cup must be above the waterline and in tanks with hoods, the hood may need to be adapted to allow the skimmer cup to protrude high enough above the water.

All skimmers need a stable water level that doesn’t fluctuate, so if your skimmer is in the main tank you’ll need an auto top-up system to set and top-up to that waterline. And in a sump, the water level in the skimmer chamber should be set by a baffle. 

For sump based internal skimmers, they need a stable water height, but also a minimum water level too, with many medium-sized models requiring a water height of 20cm to sit in. Again, plug the skimmer in and it will start to produce lots of fine bubbles inside the chamber. But this time you need to adjust the water height inside the skimmer manually so that the bubbles rise up to the base of the neck and then gradually produce enough skimmate to overflow into the collection cup over the next few hours and days. 

Most sump-based skimmers have adjustment by way of a knob or vertical pipe that you twist. Twist one way and the bubbles should rise up the tube. Twist the other way and the bubbles should drop back down. Finely adjust the bubbles so that they rise up and then stay just below the neck, which in turn is below the collection cup. If the cup fills with water within seconds, minutes or hours, the bubbles are too high in the neck and should be adjusted down.

If no skimmate is collected in the cup after a few days, the bubbles are too low in the neck and should be adjusted up. Most reefers aim to fill their protein skimmer cup with dark brown skimmate every few days, or twice a week. 

Adjust skimmers with the knob, wheel or pipe attached to the side of the body

Further adjustment

Most protein skimmers can also be adjusted by how much air they suck in. And some DC skimmers can also be adjusted by a pump controller which controls the output of the pump. Adjusting up to three things all at once can make life difficult, so we recommend that DC pumps are set to maximum, air intake is set to maximum, and then bubble height is adjusted by the pipe or valve as above. 

When skimmers go haywire

Protein skimmers can be temperamental devices which are prone to overflowing. Lots of things can cause it but it’s usually when certain foods or additives are added which alter the surface tension of the saltwater. 

The worst outcome is that the skimmer overflows outside of the tank or sump and causes a flood. But even if contained inside a sump a prolonged overflow can spray saltwater, causing cabinet boards to take on water and deform, and hinges to rust. It really can pay off to fit a skimmer guardian to try to prevent any short term floods or long term cabinet damage.  

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Jeremy Gay is an author, lifelong fishkeeper, and aquatic specialist. He's a former editor of Practical Fishkeeping Magazine, UK editor at Reefbuilders, a former aquatic store manager, and has collected fish in Sri Lanka and the Amazon. He's been on tv and radio, contributed to Koi Carp and Gardeners World magazines, been a product tester, a judge, and a product developer. Jeremy is here to guide and advise you on all things tropical, pond and marine, from set-up to stocking, health, feeding to breeding, as well as solving many common fishkeeping problems along the way.

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