I'm also using skimmer considered by most being crappy, other appreciate it, Visi-Jet (inside tank). New aquarium with not much of waste gives not much foam - exactly as was said. When bioload is usual, adjustments are mostly related to keeping level of water at certain point of skimmer body - for my skimmer it is red band (marker made by manufacturer). In reality, I have keep water level 1/4" below recommended marker - otherwise water is collected instead of wet or dry foam. This is inconvenient - even with placing skimmer as high as possible using suction cups, level of water in the tank have to be low, may be 1.5" from rim.
In your case, you can check instructions for recommended level of water and marker for it (my guess is below lower edge of transparent cap), and try place skimmer higher or lower in HOB filter, even with some DIY holders or suction caps. Changes should be seen in a few minutes (or 10-15 minutes if after feeding, oils can interfere with foam production. Use of tap water conditioner, containing
slime coat, may lower foam production at all. Last was not problem for me, but manufacturer mentioned such possibility).
Does this skimmer allow some rotation of this transpaternt top for adjusting water flow though skimmer? Maximum or 3/4 of maximum may work the best.
This dark hole on top is air intake, right? My skimmer after 2 months of work sometimes stops producing a lot of bubbles, than I push some air back through air intake (placing air tubing at it and pushing air by mouth), it works. May be this is not recommended, don't know.
Never was able to collect dark brown liquid - tea colored only, but a lot of it, what is good enough for me, only more frequently empty collection cup.
Hope, it helps. Good luck!
that is why I'm back in the hobby!!
