Just about the simplest drop checker DIY design I could think of is to plug one end of a piece of 1/2" tubing and fill it with the solution and dye. Then bend the tube into an upside down U shape and attach it to the inside wall of the tank. Or, if temp. didnt matter that much, you could have the plugged end w/ the solution hanging over the rim on the outside of the tank, and bend the open end over the rim of the tank and into the water.

Pretty simple, but not very asthetic and maybe not entirely efficent.

Or cut the tip off a plastic turkey baster and glue it into the end of a .5" tube. Then plug the top end of the tube and fill it with the solution. Kind of like what you used in the pic, but using a tube instead of a cup.

???Maybe?? I dunno. There's a million ways I could think to make a ghetto drop checker.

I sat and thought of a bunch of different ways one day, but the best looking one was the one I bought from AquaticMagic. I think their ADA knockoffs look better than ADA's actually do. :-) Just a matter of taste.

I give mine about 2 hours reaction time.

-Mike B-