Reef Octopus BH100S

I've had this reef octopus skimmer for several months. While it was on my 55 it was a beast. Stuff looked like dark tea in the collection cup. I had to take down the 55 and downsize to a 20 tall. Now I realize this is overkill for a 20 gallon tank. But I figured it would just do a better job. I used water from my 55 that was running for 8 months and some of the live rock. I did use new sand though. Problem is now the cup fills up fast sometimes and slow sometimes. But it's a little dirty but nothing like it was before. I'm sure it needs a good cleaning. The water level in the left side is a lot higher than it used to be. I think that's from the sponge is dirty. Any advice ? I'll post some pics.

 

its generally not going to be as dark because there is not as much stuff to pull out.

 

That makes sense. Less water volume now. It does need a good cleaning though. That's tonight's project.

 

And also is it even productive to run a skimmer on a 20 tall with weekly 4 gallon WC.