For the last 4 weeks I have been running my 187 gallon reef tank without a skimmer as sort of an experiment.

A few months ago I lost a number of corals due to what I believe were very low levels of phosphate in the tank. I run an ARID algae reactor and it does a great job pulling out nutrients. With the ARID you do have to dose nitrates to keep the chaeto growing and lately I have been dosing phosphates to keep levels from going too low. Ultimately, you want nitrates and phosphates at a 100:1 ratio to maximize chaeto growth.

With the ARID you can either use a skimmer or go skimmerless and let the ARID be the sole form of filtration. Ultimately, I decided to pull the plug on the skimmer.

Why I Went Skimmerless

I have been having some issues with cyano and I believe it might be due to excess C02 in the air where my sump and skimmer are located. The sump is in the same room as my furnace, a potential source of C02, and there is little to no ventilation in the room. In theory, shutting off the skimmer in this situation should lower C02 in the tank since the skimmer’s air intake will equalize C02 levels between the air and tank water. Cyano prefers high C02 so less is better.

At this point the cyano has receded a bit so my hope is that it will continue to do so. As I mentioned before, I have started to dose phosphates, another reason I shut the skimmer off since it was driving phosphate too low in conjunction with the ARID.


Currently, my nitrates are at 10 ppm and my phosphates, with the dosing, have climbed to .13 ppm, right at the 100:1 ratio I am seeking. However, I have increased the light period in the ARID to lower those levels with the hope it will help beat back the cyano even more.


Stay tuned for future updates on my skimmerless experiment.



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If you are looking for additional insights and information, please explore my many other reef tank and SPS related articles as well as my book, A ReefBum’s Guide To Keeping an SPS Reef Tank: A Blueprint For Success. Additionally, you can see all of my reef tank videos online now as well as my Live HD Webcam.


Happy reef keeping!