When I noticed my fish in distress many of the small tetras, rasboras, were at the water surface in a corner, looking like they were gulping air from the surface. The bottom dwellers hardly moved, still at the bottom, some on their side, and some of the more colorful fish had faded colors. Those signs were often combined with a dead fish shortly after.
It helps to have a good needle valve on your regulator, because you can then easily make small changes in bubble rate, and know those changes wouldn't drift higher or lower. That made it much easier to adjust the CO2 to an optimum bubble rate. With the Milwaukee regulator I had, I used the pressure adjustment, instead of the needle valve, to make small changes in bubble rate - the needle valve wasn't nearly good enough for that purpose.
Drop checkers aren't essential, and no one is required to use them. They are cheap, easy to use, and are one more tool that some people find helpful. They are not suitable for making the final adjustment of bubble rate, because they change color too slowly, and have too big a built in inaccuracy (judging the color is very subjective). Like all tools, they can make it easier to do a job.
Last edited by Hoppy; 08-04-2012 at 05:29 PM.
Reason: more to say