Filter Cups.

Our little helpers. Even compared to skimmers, filter floss cups are probably one of the least glamourous part of our tank. At least skimmers come with different features, different capacities, different shapes. The recent trend of automatic roll filters have put these guys even further down the list!

Well, we have tried some different methods and have even gone back and forth a few times. Much like our lights, this final configuration is on brand with super simple so it looks like it’s here to stay – at least for now =).

The Red Sea Reefer series, as some of you already know, has this “feature” in that it doesn’t fit the off-label 4″ filter sock/media cup sizes. You MUST buy on label or modify or source a custom maker. We COULD complain, but then we would have missed out the challenge to find the super simple solution.

What we learned: filter socks

Filter socks are great…. with some investment and some work. 100-200um filter socks come in around $4-5 a piece for the off labels. As we talked about before, we needed to modify them to get them to fit in our Red Sea trays. Once installed, time to clog (TTC) was about 4-5 days. We chose to hand wash them until we found this amazing small, portable washer unit. We just didn’t feel comfortable throwing the socks in our home laundry machine for many reasons, but mainly cross contamination.

We were tossing and replacing these socks every 2 months or so. After a while, we just got sick of washing the socks and they were more expensive than we wanted to spend for recurring maintenance.

What we learned: mesh socks

On one of the posts on, someone mentioned that they used 50-100 um MESH filter socks and they were so much easier to wash. Why didn’t we think of that?! It was brilliant and we really liked it for a long time. We even ponied up and bought the on brand socks (Red Sea 4″ mesh socks) so we didn’t have to modify anything.

Time to clog (TTC) was about a week. We were tossing and replacing them every few months after washing couldn’t keep them unclogged. But like all tank related things, we thought – could we do better?

What we learned: Red Sea filter media cups + filter floss

Ok. No more washing socks. We were done. We looked into the auto-rollers but permanent modification of our sump wasn’t in our wheel house and wasn’t something we wanted to do. Our only choice left was no mechanical filtration or filter floss.

Since the reefer does not come with a filter floss tray, it was going to be filter floss media cups. Again, we went with on brand since we didn’t want to modify anything.

4″ diameter, 8″ height
media on bottom + floss on top

We tried different iterations to try to reduce the number of times we needed to change out the floss:

  • All floss – needed a lot of floss to cover all of the holes in the cup; didn’t really change TTC
  • Bottom media + top floss – helped with reducing how much floss we had to use, but media would need to be rinsed A LOT.

With the iterations above, we missed the common sense piece (why TTC on socks lasted longer than floss) – as long as we weren’t increasing the surface area of water passing through the floss, regardless of how many layers we tried, the time to clog (TTC) was going to be the same. Duh.

What we learned: Our filter cups + filter floss

We like the filter floss way. As a friend said to me: “There’s something satisfying about putting in pure white filters in place of gunked up green ones.”

This leads us to our filter cup design and how it affects our tank set-up and maintenance. Our considerations:

  • Modifying the sump to increase flow surface area was not an option for us.
  • Clean look
  • Super simple maintenance
  • Bonus: optimization of sump space

Our cup design: Our cup is 2″ in height, 4″ in diameter. We kept the holes to just the bottom of the cup so that we can use half the amount of floss that we used with the Red Sea cups.

With the cups installed, we gained 6″ of height, which is the perfect space to stash media. Flow is not obstructed and it is super easily to pull out the media for a quick rinse/shake during water change time. TTC on the floss is about 3-4 days for us.

2″ cup height
3x more space for media

Thanks for reading and we hope that you too keep your tank maintenance super simple.

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