Help SPS STN and RTN because of new RO?

[popsock]

Hi, I have a friend who recently discovered his RO water was... well, basically 50% tap water. He's been having some algae problems, but his SPS dominated tank actually handled the tap water pretty well. Anyway, he bought a new RO unit and hasn't done any water changes at all yet.

He puts in less than one gallon per day in top up, and has experienced STN and RTN in about 8-10 colonies of SPS corals in the few days after changing the RO unit.

I'm surprised at this because the 150 gallon system has only experienced a tiny amount of new water, so what do you think is the cause of this sudden problem?

All other water params are very consistent, nothing else seems to have changed at all.

I have one idea but I'd like to read your ideas please.

 

[bigswaug]

There can be many reasons.. What are your perams?

 

[popsock]

Perams are all good, haven't changed in 18 months and have been doubled checked by 3rd party.

 

[ros_sco]

Could be that the less than stellar previous RO water caught up with him at the same time that he noticed and decided to switch. Meaning maybe the damage was already done?

 

[cal3v]

Was the new membrane flushed properly before use? Is there a DI cartridge after the RO membrane?