What colour is the water you remove from the system when you do your water changes?

I've discovered that in tanks I'm not skimming, the water I remove is kind of yellow. In the system I skim, the water I remove is colourless.

It's pretty clear.

I think the problem is water is not getting into the skimmer very easily so it is just skimming same 50ml of water over and over. I need to add some holes up the side of the reaction chamber below the surface to allow water to flow through easily but I fear the micro bubbles will just escape.

In a conventional air operated skimmer how do you get new water into the reaction chamber?

Are you still using this skimmer? Did you drill the hole higher if so what happened lol?great idea