High Phospate

water changes and GFO

 

Your RO system is for drinking water. For reefkeeping, you really should use RODI water (Reverse Osmosis Deionized). The DI is a final stage where the water is passed through a bed of resin that removes ions that the RO membrane cannot remove.

For instance, my RO filter will knock my tap water TDS down from over 500ppm to about 10-13ppm. All those ions are a mixture of things, but imagine if 10% of that is phosphate. That's 1.0ppm phosphate in your RO water.

I would recommend getting a dedicated RODI system for just your reef, because your drinking water RO system likely has a pressure tank and this is not what you want to use. As your pressure tank fills up, the water pressure on the production (effluent) side of the membrane increases and this allow more ions to migrate. So at the point where your tank is nearly full, and flow stops, the concentration of ions on the effluent side of the membrane skyrockets, and then when you take out a glass of water, all of that flushes into the pressure tank when production starts up again (to replace that glass of water). So your pressure tank will likely have something like 100-150ppm depending on your system. All ions, no problem for drinking water, but do not use this for your tank.

Having a dedicated RODI that only runs when you need to fill your RO holding tank (like a BRUTE trash can or another unpressurized holding tank) is what you want. Maybe a float and a automatic cutoff switch, but that is just so you don't overflow your holding tank. Once the flow is stopped by the cutoff switch, you should flush the membrane before trying to make more RODI, for the same reason - once flow stops, ions build up on the production side, and when you start production again, all that high TDS water goes straight into the DI and burns it out fast if you keep repeating this.

As for GFO, be careful that you don't drop it too fast. GFO will do that, and changing things too fast can cause problems too. Start by fixing the source of the phosphate, then a little GFO (even in a mesh bag in the sump, no need for a reactor right away)

Also gotta ask - are you seeing problems in the tank because of the high phosphate? I know people (big names in the industry) who run 1.0+ ppm phosphate and their tanks are fine. Stability is the key. Keeping phosphate at 0.000 is a mindset that created an whole sub-industry so don't freak out.

 

Phosphate Rx is Lanthanum Chloride (LC). They don't make it very clear that it is that. If you google LC you'll see lots of varying opinions on it.

LC chemically binds phosphate and causes it to precipitate out. Some say that you're supposed to drip it into a 5 micron filter sock so that whatever gets precipitated out will get trapped by the filter sock, otherwise it clouds up your tank (temporarily) and some corals get real ticked off when you use it.

It definitely does the trick of eliminating your phosphates instantly, but I still don't fully subscribe to the mindset that you want to run 0.0000000 phosphates.

Dropping Phos from 0.128 to 0.000 instantly could cause a backlash.

 

I just tested my water with my Hanna meter:

Tap: 554
After membrane: 10
After DI: 0