Overall, in our opinion, not much.
Still fish and corals in a glass (or acrylic) box filled with water. For the animals to survive and thrive, the goal is “clean”, balanced saltwater and the strategy as we see it remains the same, water changes.
The frequency and amount of change depends on your bio-load, your acceptable loss policy, and budget (time and money).
For us, the sweet spot was 10 to 20%, every week or two.
Do I need a skimmer for my basic mixed reef tank? For our KIS system, the answer is no. The negatives include initial expense, noise, electricity consumption, heat, and possible leaks.
For us, there is no substitute for water changes, so we removed the skimmer and have not looked back.
Exactly what does a skimmer remove? The bad stuff? Some good stuff?
General consensus seems to prefer the smaller ROX carbon (on the right in the picture). About the size of tips of lead pencils.
Note that we tried carbon in our KIS System and removed it. We did not see any noticeable improvement (or degradation) in water quality or livestock with carbon in place.
Orphek is out with another model in their Helix line.
Our overflows are gravity fed to the sump and end-up in a filter sock. We get some skimming action from the agitation of the water in the filter sock. We just wipe the suds away with a paper towel.
Our skimmer was shut down at the beginning of the KIS System evaluation period. The benefits of a skimmer are questionable and the problems numerous which include: cost of the skimmer, heat, noise, electricity use, and potential leaks to name a few.
In our 180L system, we have been following a 5 gal water change per week schedule which translates to roughly 10% of system volume (taking into account – for live rock and + for sump) per month.
Assumption: Water quality is always degrading.
By that, we mean as far as the animals in our closed system are concerned, things are always getting worse! The good stuff like essential minerals and trace elements are being depleted, and the bad stuff, pollutants, heavy metals, are building up.
A number of small water changes are slightly less efficient than a few large changes. Published studies indicate for example that one 30% change is the equivalent of a 26% “continuous” change. With many small water changes you are obviously removing a little of the new water.
The advantages of small water changes include (1) less stress on the animals, (2) usually easier to do, so less stress on the reef keeper, (3) doesn’t change the water levels in the tank, (4) can often be done without shutting-off the return pump(s).
DISCLAIMER: We are not commenting on or making assertions about the marine biology, chemistry, physics, thermodynamics, biochemistry, or biophysics of a saltwater aquarium — a closed system. 🙂
The system is up and running. After a fair amount of reading and research, we have decided on a regimen of 5 gal water changes weekly. That gives us 10% monthly based on a 200 gal system (approx, display tank + sump).