A properly maintained and cycled tank should never need one of those "ammonia alert" cards. Those things are expensive, inaccurate, and can fall apart in your tank and make a mess. It doesn't hurt to test for ammonia from time to time just to make sure things are running smoothly, but the only reason there would be an ammonia spike in a mature tank like that is 1) ammonia is coming out of your tap so you're adding it with water changes 2) there's some source of excess ammonia in your tank, due to overfeeding or a dead animal somewhere in the tank.
If you keep aggressive cichlids, I strongly recommend that you have a cycled tank set up as a hospital tank. If you can't keep it cycled, at least have one ready to be filled with conditioned water, and keep a sponge filter running in one of your display tanks. When a fish is sick or injured, move it and the sponge filter to the hospital tank for treatment. Many cichlids are mean fish, so even in ideal conditions you sort of have to expect to have to deal with fights from time to time. If the injuries aren't too bad, something like Melafix can work wonders with regrowing lost tissue.