Question
Algae forms so fast in my saucers that I fear for my plants. I use bleach to clean the saucers frequently; but is there a better way?
Does the presence of algae tell me something important about the quality of my water?

One more question? What else beside aphids have a symbiotic relationship with ants; or are ants a positive indication of ONLY aphids?

Thanks, Carole

Answer
Algae grow where there is moisture and sunlight. If your saucer is clay, change to plastic. Clay will hold the moisture, where plastic will dry out faster. Don't let water sit in the saucer. (It is not good for the plant to sit in water either.) The algae won't hurt the plant, other then it is another plant competing for nutrients. But it would not use enough nutrients to cause any noticeable difference. The best way to clean the algae is with bleach, but be sure you rinse it thoughly, because the bleach could harm your plants if it gets up into the roots and burns them. I don't think it is your water  that is  the problem, but the enviroment. The combination of moisture and light. Correct those two things and the problem is solved.
Ants are attracted to sweet things. Aphids produce a sticky, sweet, residue, called honey dew. That is what attracts the ants. They don't care about the aphids, just the honey dew. Aphids are the only thing I know that produce honey dew.
The only plant, I personally know about, that attracts ants, without aphids, is the Poeny. It has a sweet sap that the ants enjoy.
So if there is a sticky residue on the leaves that the ants are on, you have aphids. Soapy water every few days along with a good spray rince with the hose, will help a lot.