High Alkalinity, Dont Know Why

[violatorv]

CAN YOU HELP ME PLEASE ; MY ALKALINITY IS VERY HIGH IN THE WELL 0VER 300 RANGE, MY NITRATES WONT SEEM TO DROP BELOW 40 PPM ,MY NITRITE IS AT ZERO, I HAVE THE CALCIUM AT 460, MY PH IS 8.4
i HAVE HALIDES AND A EUROREEF SKIMMER AND CIRCULATE ABOUT 800 GALLONS PER HOUR ON A SEVENTY GALLON TANK,BUT THE CORALS REALLY DONT GROW AND IM NOT GETTING ANY GROWTH OF CORALINE ALGAE
NOW IM STARTING TO GET THAT SILKY LOOKING FILM ALGAE
SNAILS DONT SEEM TO DO WELL EITHER
I ATTEMPTED CHANGING ALL THE WATER AND CLEANING THE ROCK AND PUT NEW SAND BUT IT CAME BACK TO THE SAME PERAMITERS
I SET UP A SECOND TANK AND GOT THE SAME ALKALINITY PROBLEM THE NITRATE HAS ALREADY GOT DOWN TO 20PPM ON THAT TANK
THE ONLY THING THAT THE TANKS HAVE IN COMMON IS THE SOURCE WATER BUT IT IS OUT OF AN REVERSE OSMOSIS UNIT AND I HAD THAT TESTED AND IT CAME OUT ZERO ON NITRATE AND ZERO ON HARDNESS 80 PPM ALKALINITY AND VERY LOW ON PH BELOW 6.4 PLEASE GIVE ANY IDEAS THANKS

[Randy Holmes-Farley]

Do you dose anything?

The top off water from the RO had 80 ppm alkalinity? That seems very high and may be the explanation if demand in the tank is low.

[0 Agios]

what are you using to test alc ?

[demonsp]

Whats used for water flow?
How does your SB look?

[violatorv]

HOW DO I UP DEMAND FOR ALKALINITY

[Randy Holmes-Farley]

Hard coral and coralline algae growth is the primary demand.