I have the water feeder (not sure if it is called that) below (photo from antshop.ch), it has a synthetic sponge at bottom. It is OKish but requires being careful to not push the cylinder too much inside to not block the water, so everytime I refill it I am worried if it is working fine. I thought maybe a test tube with just water and closed with cotton would work and I am trying this now. However, it seems ants prefer the water feeder not the test tube. They also try to pull out the cotton threads in the test tube. So my question, is there a best way to supply water to the ants in the outworld ?