yes sir carb you can still use the filtered water into other purposes. that doesn't mean na toxic na ung filtered by-product. I think plants would greatly benefit from the minerals filtered from the RO system, so pwede mo pa siya pandilig
but not to the extent that you will use it to your tank cause it will defeat the purpose ng pagfilter mo. Usually the TDS of rejected water from RO is 800-1500 PPM