Water changes - why?

Originally Posted by Navanod

Normally, the most obvious purpose of waterchanges are to remove excess nitrate.

However, there're alot of other parameters that we seldom or never measure, such as total dossolved solids (TDS) and all the trace minerals.
These will slowly build up with time without waterchange, and reach toxic levels eventually unless the plants are really taking up everything.

In nature, rain is similar to a waterchange and that triggers breeding and molting for certain species. Thats maybe why molting is seen after waterchange

you sir, are pro. I'm buying your argument