Desorbing phosphate from sand with lanthanum.

[Garf]

Wife's Tank. lol

Yes, she likes to keep things clean

Here’s my tank;

 

[taricha]

Imagine using the regeneration method with GFO instead of sand. Would the GFO have more surface area than sand to adsorb more PO4?

For me, the appeal of this method is avoiding GFO and only introducing aragonite sand which is already common to a tank.
(And small amounts of Lanthanum, but already attached to solids)

 

[taricha]

Oh, while we're on the topic, what do we predict would happen to Silicate from the tank water in this process?
(Does it attract to aragonite like PO4 by similar mechanism?)

 

[Miami Reef]

For me, the appeal of this method is avoiding GFO and only introducing aragonite sand which is already common to a tank.
(And small amounts of Lanthanum, but already attached to solids)

For me, it’s to save money instead of repeating buying GFO, but to have a similar efficacy as GFO. I use high capacity GFO, and it works like a beast. I can’t imagine coarse sand outcompeting it when comparing the same volume.

I personally had no issues using granular ferric oxide in a tank. The worst IMO is some soluble iron escaping which can even be a good thing for corals and macro algae.

I feel like I’m in the minority as I never had issues with GFO. I just don’t understand how GFO can harm corals so long as PO4 isn’t pushed too low.

Oh, while we're on the topic, what do we predict would happen to Silicate from the tank water in this process?
(Does it attract to aragonite like PO4 by similar mechanism?)

Randy answered this question already here: https://www.reef2reef.com/threads/does-silicate-bind-to-rocks.1030048/

 

[Randy Holmes-Farley]

Randy answered this question already here: https://www.reef2reef.com/threads/does-silicate-bind-to-rocks.1030048/

I was just formulating a comment on that. Luckily, it’s the same as before. lol

 

[areefer01]

For me, the appeal of this method is avoiding GFO and only introducing aragonite sand which is already common to a tank.
(And small amounts of Lanthanum, but already attached to solids)

LC use or the sand?

 

[taricha]

LC use or the sand?

I think the aragonite sand is the attractive part, using that to lower PO4 has been an appealing idea to many. But Garf's lanthanum regeneration cycle (to quickly pull PO4 back off the sand) seems to be what actually allows the GCCM to work to remove practical amounts.

 

[Garf]

I've decided to restrict pH to around 8.4 (for now) in this tank. I've included it in this thread as the addition of CO2 immediately before the bag could have implications (yes, I could change this, but don't want to, yet). CO2 is produced using yeast and sugar and is controlled by sucking the CO2 through a small skimmer pump, activated by my trusty weipro pH meter. Success with this prototype may be celebrated by upgrading the plastic yeast bottles to full on Jack Daniels bottles. I consider this method to be "Trickle Charging the Carbonic Acid Battery", lol.

 

[taricha]

the addition of CO2 immediately before the bag could have implications (yes, I could change this, but don't want to, yet).

Eh, maybe not ideal. If the co2 goes into the system right at the aragonite bag then some of the CO2 may not be bringing down the water pH, but instead dissolving the aragonite.
(If the co2 is well mixed with the water first, and the water pH isn't in the 7's then aragonite dissolution is not a concern. )

 

[Garf]

Eh, maybe not ideal. If the co2 goes into the system right at the aragonite bag then some of the CO2 may not be bringing down the water pH, but instead dissolving the aragonite.
(If the co2 is well mixed with the water first, and the water pH isn't in the 7's then aragonite dissolution is not a concern. )

Yeah, I'm hoping I've learned a lesson or 2 from my algae scrubber CO2 experiment 11 or 12 years ago. Grew algae like stink, and dissolved everything made of calcium carbonate down the one end of the sump, lol.

 

[Garf]

Seems I can achieve the goal of preventing tank pH from from going over 8.4 and maintain the sand bag effectiveness using CO2. The sump section where to CO2 is added doesn't go lower than 8.25 during operation, I think in part because I've added the skimmer body to the skimmer pump (no skimmer cup). Phosphate reduction doesn't appear to be affected (0.15 ppm Hanna today).
As a side note I've decided that adding bicarb in to the sump in one "glug" is not a good idea. I was adding it into the section where my CO2 enters the water and it was needlessly adding CO2 by sending the pH high. After experimenting with adding the bicarb into the return pump section, I noticed bad effects. So, back to adding it into my 1.5% waterchange which is dripped in over the day (I may get another dosing pump one day, lol).