Are DC protein skimmers King? Advanced control & tuning by changing pump speed? | BRStv Investigates

Through the latest series of BRStv Investigates experiments we have been studying protein skimmer performance with the goal of finding some more usable information about tuning protein skimmers to help you make the best selection for your tank and ultimately get the best performance possible from your skimmer.

We started our experiments by looking at the effects of water depth and flow through rate on air draw of the three most common types of protein skimmers found in home reef tanks, single pump AC skimmers, single pump DC skimmers and dual pump recirculating skimmers. This was broken into two seperate videos based on the skimmer price range, $150 - $250 and $250 - $400.

Next, we looked at the ease of tuning and ability to perform under varying conditions by comparing performance between single pump internal skimmers (both AC and DC pump driven designs) vs dual pump recirculating skimmers. That episode taught us that recirculating skimmers are much more efficient at maintaining a steady foam head regardless of water depth and flow through rate. This was key to our future developments and really reduces the risk of finicky performance and eliminates the need for constant tuning.

As usual with our BRStv Investigates series, each test raises more questions and in the 4th episode we tested the best method of protein skimmer adjustments to achieve wet or dry skimmate. Among our tests so far, this was definitely the most enlightening episode because most of us are doing it wrong. Don’t beat yourself up though, the manufacturers tell us to do it wrong 99% of the time.

What it boils down to is using the outlet pipe to adjust foam level and flow through rate will not give you optimal performance. You first need to tune the amount of air going into the pump to create the wet/dry foam you desire. Then adjust the foam level to achieve and efficient rate of collection into the cup.

From our testing using a DC recirculating skimmer to do this appears to be the most reliable method. Simply because we found that adjusting the air draw alone on a single pump AC skimmer affects several other variables that make optimal tuning more difficult to get right.

What if we combine the two approaches to air draw adjustment using the adjustability of a DC powered pump with the single pump skimmer design? Would we be able to create similar dry & wet skimmate foam as we did with a recirculating design without the second pump and without sacrificing tunability?

Those questions and results lead us to our latest experiment, where we aim to find whether or not a single pump DC skimmer has the same range of control as a recirculating model.

The Experiment

We chose three Skimz SN167 DC single pump skimmers and placed them into separate tanks running at different pump speed starting with the lowest setting 1 on the left, middle speed setting 10 and finally the highest speed setting 20 on the right.

Water depth was set at 9.5” and foam level was equally level across all three of them. We added 5mL of organic waste from other skimmers around the office at 10 minute intervals to observe how the different pump settings affected the type of foam and ultimately waste collection.

In the second test using the same pump speed settings and organic dosage, we actively tuned the water level inside each skimmer as we dosed the organics which is more representative of how most reefers would use them at home; adjusting the foam level to achieve constant or efficient collection.

The Results

The first round of testing with equal internal foam level across all three skimmers produced results similar to last week. The higher velocity of air in tank 2 and 3 pushed the foam bubbles all the way through the neck and up into the collection cup and produced a lighter colored mixture of organic waste and water.

Test tank 1 with the slow pump speed and lower air draw creates a substantially longer dwell time but was not strong enough to push the foam up into the cup for collection.

For test two we repeated thttps://www.bulkreefsupply.com/video/view/brstv-investigates-single-pump-dc-protein-skimmershe same settings and dose of the organics, however, this time rather than just monitor their foam production we actively raised or lowered the water level to adjust for efficient collection.

As the test progresses the time lapse reveals that we needed to raise the water level inside test tank 1 in order to get the thick dry foam to raise up into the skimmer neck while in test tank 2 and 3 we had to lower the water level in order to keep the cup from overfilling.

Keep in mind that these settings are specific to the organic load we put in these tanks. It’s important to note that the adjustability of the DC pump allowed us to adjust the air to the amount of organics in this test, which is something you can do on your own tank where we all have different amounts of fish and food.

Does a single pump DC powered skimmer provide us with as much control and tunability as a recirculating DC skimmer design?

We rate this a 7/10 because although having a single pump DC skimmer does provide us with more control over the type of skimmate foam the skimmer produces. There are, however, factors like operating depth or water height in the sump that will absolutely have an effect on performance which needs to be accounted for when tuning whereas with a recirculating skimmer design the operating depth just isn’t an issue.

The single DC pump skimmer is easier to adjust over a single AC pump skimmer, but falls short of the truly configurable options like the Regal 200EXT DC recirculating skimmer we also tested.

We plan to take what we’ve learned about tuning the air draw rate and put it to the test on a real world tank full of fish and SPS corals, the Red Sea Reefer 750XXL tank we built as part of the BRS/WWC Hybrid build. This video series is the most complete guide to successful SPS dominant reef tanks and what we feel is the only guide you will ever need so check it out!