additive

I don't use the sink in my E-25 very much, just for rinsing out glasses or emptied beer bottles, water for hand washing, etc. What can I add to the tank to keep the water fresh?

The Universal 25 on my Ericson 32 (1986) is about to give up the ghost. The compression is low in one cylinder (105) making it difficult to start. It is also leaking from every nock and cranny. It is my intent to replace the engine. But the cost (about 10K) will require me to wait a bit on...