My tank is almost a decade old, and never ran a skimmer for many years. There is a lot of phosphate and algae, and the overall water quality is poor. I have the SRO-RPS-2000ext (its external) and I tried setting it up, and no matter how low or high I made the air and water intake pumps, the skimmer still went crazy and overflowed. The only thing that was in the water was the water pump, I say that because a lot of people say that the water level makes a difference. What’s going on?
I am confused, you said this is an external skimmer and its external, yet the water pump is submerged? Or did I read that wrong? If it is in your sump leave it wide open and let it overflow until it calms down. You can also speed up this process by running your skimmer in a bucket with some vinegar/water mixture which helps remove any oils/residue from the manufacturing process. If it is actually set up externally like not in a sump just on the ground or something then I would recommend putting it in some sort of bin or container so that it can overflow into there. I never thought about how you would break in an external skimmer until now. It is probably a good idea to keep it in some sort of bin anyway just in case it overflows down the road as well.
Once the skimmer calms down, then you start the tuning process.
1. First you adjust the water height within the skimmer. Everyone has their own preference/recommendations for this but me personally I like to run the water level about 3/4 the way up the neck of the skimmer. A lot of people prefer to run it about half way up the neck of the skimmer, some lower and others all the way up right below the collection cup. It also depends on the skimmer (manufacturers have their own recommendations) and the water level the skimmer is submerged in (not necessarily a factor in your case if external), so you'll just have to play with it, but initially pick a spot and leave it there. I would try to find people with the same skimmer on here and ask them how they tuned it/have it set up, although your situation will not be identical it will probably be pretty close.
2. not sure how your skimmer works but on mine the next step is to adjust the airflow into the skimmer (either by opening or closing the volute or i guess in your case adjusting the height of the air pump if it doesnt have some sort of control knob or volute). The idea here is to make the bubbles as small as possible while still producing skimmate. You should wait at least a few hours but ideally 12-24hr between these air adjustments to allow your skimmer to adjust.
3. after you have your skimmer producing skimmate and the bubbles right up below the foam head are pretty small (1/8" max), you can then adjust the water level again slightly up or down to fine tune the moisture level of your skimmate. lower the water level to make it more dry, or raise it to make it more wet. Again, wait a few hours between these adjustments.
If during this tuning process the neck of your skimmer/neck of the collection cup gets really dirty/gunked up, you will have to clean that out before continuing further, because it will impact how the skimmer performs and will not be an accurate representation of the results you will achieve with those settings. You dont necessarily have to take the skimmer apart but just whipe it clean with a wet paper towel or something. then let it resume operation before making any further adjustments.
I would also check out youtube beforehand to see if there are any videos about tuning your specific skimmer. If not just watch some videos on setting up/tuning a skimmer in general like these two:
