i'm sure tom has forgot more than i ever knew. 25 vs 1.026 isn't important. i'd maybe check refractometer against a lab grade solution. check tds . add di if you haven't already. i'm assuming you have rodi, not ro . bacteria cultures are tricky, outsmarting one takes work. i'd consider a conch or three, manually remove as much as possible, and maybe do a big *** water change. spring cleaning of the sump and equiptment shoundn't hurt. i agree with tom , poop accumulations are a probabale culprit. maybe give a good powerhead blast to shake it up. tom at the reef shop uses tap water and does great. he also is a big fan of the bigasswaterchange.