Skimmate, more than just a sludgy mess…

I have often wondered what the grungy gray gunk that filled my humble remora skimmer cup could be. It was frothy on the top, liquid in the center, and sludgy on the bottom; all of the characteristics of my favorite iced mocha really, yet far from the same flavor. It really has multiple textures and a plethora of funky-fresh smells. So what could this disturbingly pungent pool of excrement really be? Luckily, I have wicked sweet google skills and there are chemists out there that love to get their hands dirty.

Ken S. Feldman published a brilliant study breaking down the exact components of skimmate titled Elemental Analysis of Skimmate: What Does a Protein Skimmer Actually Remove from Aquarium Water? This exceptionally detailed study can be found by visiting our friends at AA. I recommend checking it out if you really want to understand Ken’s genius, but if you are more into the cliff notes version read on.

Skimmate is composed of less organic material than one might guess. In fact only 34% of the skimmate was organic material or fishy number twos.

In summary, the skimmer is pulling out a solid, water-insoluble mixture of compounds that consist by weight of (approximately):

• 44 % of CaCO3
• 5% of MgCO3
• 11% of biogenic opal
• 4% of organic material
• 0.5% of phosphate

Now clearly, this breakdown is very complex and most of us will never understand it, but it can be used to truly impress our fellow reefers at our club meetings, so use it wisely!