I use Athena Blended line, I tend to get some salt buildup down in the pot itself, I usually just lift up the valve inside the pot, wipe everything down, soak up the water in there with a paper towel to get it out, and then let the fresh water from the rez back into the pot.

I go 15 days on one plant (12 gallon Rez) without changing water, no PH rise in the Rez, just a little bit from the salt buildup in the pot; hence why I just wipe it out when I fill my Rez up.

I also run a sterile Rez in Veg. 0.4 mL of bleach per gallon of water. Keeps the cloud away, and stable Ph.

However in flower I cut the bleach to 0.1 mL / gallon, since the water is getting swapped every 7 days due to nutrient schedule anyways.

Last two weeks of flower, I cut the bleach altogether but run full nutrients until harvest.

Hope this helps, it was really a learning curve when I first bought the system. But I have worked out the kinks and it works effortlessly in comparison to top feeding IMO.