To cover all bases you should really dose your RO water with prime as a RO unit does not guarantee complete removal of the water supplies dechlorinator. The big boy reefers sometimes dose their stored RO water with dechlorinator and sometimes Amquel (for ammonia) in case there is an issue with the water and/or RO system.
The RO issues are:
1. If incoming water is treated with chlorine and hopefully you are frequently replaced incoming RO carbon filter, it will successfully remove the chlorine before the membrane. If your carbon filter is exhausted (hope you are monitoring its usage ????) chlorine gets through and destroys the RO membrane and gets through into the RO output water. Some big boy reefers check RO with chlorine test kits (swimming pool test kits
) before putting RO into their tanks.They pre-store the RO water first and test (and remineralise & salt) before putting into their tanks. When marine fish cost £300 each, it pays to check the water and always add Prime and/or Amquel+.
2. If incoming water is treated with chloramine there are bigger issues. If you are using an incoming Dechlor+ carbon filter (and not exhausted) this slower flow carbon filter will break down the chloramine to chlorine and ammonia and absorb these in the carbon and all is OK. However, if flow is too fast and/or prefilter exhausted the ammonia will not be absorbed and pass right through into the RO water. If you are using a normal carbon filter is may/will possibly let ammonia through anyway. Big boy reefers again check their stored RO water for ammonia before use or just bung in Prime and/or Amquel+.
It has been reported many times in the reef forums of people using RO water wiping all their fish out due to these issues.
Output DI resins can help alleviate the above problems, but again the resins have to be in tip top condition for them to work. Or just bung in Prime and/or Amquel+.
I found out this from local fish shop as the owner was showing me his equipment
and I noticed test kits near the RO storage containers. This was to test the stored RO water for presence of chlorine or ammonia. And yes he had found chlorine once in the RO water due to a faulty filter, he assumed water was getting past the filter somehow. Anyway never had any issues, just change the incoming Dechlor+ filters and DI resin regularly and no problem.
On a slightly different note, many people have tried automating their water changes but all end up with severe detritus issues. When you manually change 50% water you end up wafting the plants around, stirring up the gravel and generally lifting all the settled detritus up and removing it from the tank. How are you aiming to do this with your automatic water changer ? There was one guy, here I think, made a rig that wondered across the top of the tank (3000litre I think) squirting jets of water down stirring up the detritus during water changes.
Also if doing automatic water changes you must must must must have a weir overflow cut into your tank. This is in case it all goes wrong and incoming water does not turn off during a system failure and prevents you flooding your room.