Auto Water Change ideas???

[Milad]

ive been racking this in my head over and over and over since i started looking into reefing.
Everything seems smiple except for adding salt. If there were salt "packets" that realesed salt little by little then you could do an automatic water change.
im thinking like those things you put in your toliet that clean it, and they slowly dissolve.

i think the key here is finding something to add salt, not do the water change.