Well this is a little embarrassing...
by
, 10-23-2013 at 03:57 PM (13504 Views)
For the past three months, my reef has been suffering from elevated phosphate levels. I've never had such a roller coaster, with the numbers rising and then falling as I treated to drop them again. Last night I did a lot of water testing.
a) First I tested the 215g reef to check the levels.
b)Then I checked the 400g that is full of water, sand and live rock to know if the parameters were close enough for livestock transfer and to make sure it wasn't cycling. The rock had been exposed to air for nearly a week.
c) Finally, I tested the 250g of newly mixed saltwater in the poly tank since it was a completely different brand of salt.
Using the Hanna Low Phosphate Checker, I was really surprised to see PO4 in the new batch of saltwater. I could understand it being in the 400g since the rock might leach out PO4, although it has been in water circulation for more than three years in a barrel without any food whatsoever. Doubting that a new batch of salt would contain PO4, I decided to test the Phosphate level of the RO/DI water. Testing it twice in the past 12 hours, I got measurements of .06 and a measurement of .09 with the Hanna Checker.
Now that I'm aware of the source of the phosphate (which wasn't my feeding at all, but rather via top off water daily as well as through water changes), I need to resolve it. I'm going to do some more testing, but my initial thought is that perhaps I'm running my RO water too quickly through the DI resin. I have three membranes with booster pumps running into the DI stage at 0.3-gallon per minute. Normally a 100gpd system runs at 0.06-gallon per minute through the resin, and 150gpd equals 0.1-gallon per minute. Adding a second DI isn't cost-effective nor a solution, as the first DI can fill up and later leach back out into the second DI's resin, wearing the second one out more quickly. With high flow rates, water can channel through the DI resin instead of flowing over all the beads individually.
The filters are two months old, the DI resin less than a week old, TDS measures 0. The membranes are about 14 months old. The TDS prior to the DI is 16. So, that leaves flow rate as a probable cause. Like Tim the Toolman, I figured more power is always better but I may have discovered a drawback.
I can't believe I didn't think of this sooner. Since we want our reef's water to measure at .02 or less, adding water that is nearly .1 everyday is problematic. I'll be sure to update you with what I discover.