Hey I was just noticing something with your system, with your bulkheads being so high up on the bucket do you have a lower drain valve or a bottom suction fitting inside one of the buckets? That was one of my issues is that I cant just drain my system all the way, there is always the last bit of water in the bottom below the bulkhead. I have thought of a couple different ways to deal with this, first what I have done in the past is just drain it as much as I can then fill again with plain water and drain and repeat, then on the last one actually get in there with a cleaning cloth and get any of the remaining salt out with that. Second I have thought about trying a bottom suction fitting to attach to the inside of my bulkheads, however I don't know if I like the idea of the pump sucking up the sediment on the bottom and recirculating that. So how are you getting all the water out of your RDWC my bro
You could try a filter bag. most any hydro shop will carry them.