Aragonite Sand And Phosphate Adsorption

jda · Jan 31, 2023

I know a guy with about a 90 gallon tank with high po4. He added 1 drop of raw SeaKlear a day for like 8 months and his tank went from like .75 to .05 po4 over that time (high enough that Chaeto struggled to grow). He just added it to the overflow with no socks (that I know of). Some will get skimmed and some will settle. With socks, you can get most of it... I imagine.

This can be significantly cheaper and easier than using GFO - bottle of the stuff and a glass dropper bottle off of amazon. Shake well before using.

Garf · Jan 31, 2023

jda said:
I know a guy with about a 90 gallon tank with high po4. He added 1 drop of raw SeaKlear a day for like 8 months and his tank went from like .75 to .05 po4 over that time (high enough that Chaeto struggled to grow). He just added it to the overflow with no socks (that I know of). Some will get skimmed and some will settle. With socks, you can get most of it... I imagine.

This can be significantly cheaper and easier than using GFO - bottle of the stuff and a glass dropper bottle off of amazon. Shake well before using.

The wife has a yellow tang in my tank, if I kill it I’m mincemeat, hence the remote bucket regeneration idea. I wonder what effect lanthanum would have with GFO?

jda · Jan 31, 2023

There are some really good hobbyists who have noted significant fish losses using the stuff in the tank. Many other really good hobbyists have reported none. There is enough here for me to be cautious since these were smart, experienced folks who you can trust and not some thumb suckers doing crazy stuff off of social media videos. My guess is the concentration matters if you could measure or dig in - flocculant irritating or plugging up gills? If you use socks in the tank, the fish appear to always be OK.

My guess is that the LC will scavenge the water column of po4 quite quickly and if some of that water gets near the GFO, the GFO will release some po4 back to equilibrium. You want the rock and sand to release, not the GFO, so I would get it out of the tank.

On another note, heard that Hawaii lifted the commercial fishing ban yesterday and that permits are supposed to start being issued in a few weeks. Yellow Tangs for everybody... unless more legal appeals to a higher court happen.

Dan_P · Jan 31, 2023

Garf said:
Would Lanthanum in a remote regeneration bucket pull a lot of phosphate off the calcium carbonate? Then rinse (or filter out) to remove lanthanum precipitation. If so I’m guessing the really cheap stuff would suffice as it’s not going in the tank anyhow. In particular thinking about removing the fluidised sand filter in its entirety from the tank, plopping in a bucket, running with an excessive amount of cheap Lanthanum, rinsing in RODI, replacing on the tank. If the adsorption / desorption is as fast as it appears, multiple runs could be made in short order if required.

The part of this question I can comment on is the desorption rate. For sand, it reaches equilibrium in less than 30 minutes. I have done a little work on aragonite reactor media, chunks of aragonite, and found reaching equilibrium to be very slow but the amount of phosphate adsorbed surprisingly was about half that of sand. The implication is these chunks are porous. Desorption was also slow and oddly very incomplete compared to sand.

Garf · Feb 4, 2023

Now, I’m pinning my hopes on that kalk does actually precipitate calcium carbonate onto sand due to high pH, incorporating phosphate (sand clumping). What I can state for sure is that when my pH goes above 8.5, the tank becomes slightly misty. I’ve been restricting pH until this last week but now upped the pH, see what happens.

Garf · Apr 4, 2023

Finally started a deabsorption test on sand from my sand filter. 1.8kgs calcite, 5.4 Litres new saltwater tested @ zero. Method as previous, circulated with a small power head, occasional stirring with the long end of a big mallet, lol. Sand had been exposed to my display for a week with a phos level of 0.65 ppm.

15 minute deadsorbtion. 0.16 ppm
2 hrs. 0.22
26 hrs. 0.29
48 hrs. 0.42
96 hrs. 0.45

That’s all for now.

Randy Holmes-Farley · Apr 4, 2023

Garf said:
Finally started a deabsorption test on sand from my sand filter. 1.8kgs calcite, 5.4 Litres new saltwater tested @ zero. Method as previous, circulated with a small power head, occasional stirring with the long end of a big mallet, lol. Sand had been exposed to my display for a week with a phos level of 0.65 ppm.

15 minute deadsorbtion. 0.16 ppm
2 hrs. 0.22
26 hrs. 0.29
48 hrs. 0.42
96 hrs. 0.45

That’s all for now.

Interesting, thanks.

Dan_P · Apr 4, 2023

Garf said:
Finally started a deabsorption test on sand from my sand filter. 1.8kgs calcite, 5.4 Litres new saltwater tested @ zero. Method as previous, circulated with a small power head, occasional stirring with the long end of a big mallet, lol. Sand had been exposed to my display for a week with a phos level of 0.65 ppm.

15 minute deadsorbtion. 0.16 ppm
2 hrs. 0.22
26 hrs. 0.29
48 hrs. 0.42
96 hrs. 0.45

That’s all for now.

How big is your display tank? I would like to do some figurin’.

Did the display tank PO4 decline or stay the same?

Thanks!

Garf · Apr 4, 2023

Dan_P said:
How big is your display tank? I would like to do some figurin’.

Did the display tank PO4 decline or stay the same?

Thanks!

200 litre, yes it dropped 0.1ish, as previous. I would add that there was a lot of detritus trapped in the sand. I’m running it fluidised now (barely) so the crap should flow through.

Garf · Apr 6, 2023

After 120 hrs, reading stayed the same so assumed equilibrium was reached. Reset the test with 5.4 Ltrs new saltwater, after 24 hrs got a 0.33 ppm reading, higher than last time (presumably testing variation, maybe). Appears there’s still plenty of phos left on the sand to desorb. Will be starting a Lanthanum regeneration thread soon.

Dan_P · Apr 8, 2023

Garf said:
After 120 hrs, reading stayed the same so assumed equilibrium was reached. Reset the test with 5.4 Ltrs new saltwater, after 24 hrs got a 0.33 ppm reading, higher than last time (presumably testing variation, maybe). Appears there’s still plenty of phos left on the sand to desorb. Will be starting a Lanthanum regeneration thread soon.

Based on the aquarium data, 20 mg of PO4 was removed. From the desorption data 2.4 mg of PO4 was desorbed from the sand.

You are correct that the sand reached equilibrium, but that does not mean the PO4 was completely removed, as you found out. Rather, the desorption stopped when the concentration reached 0.45 ppm. If the volume of water had been larger, more PO4 would have desorbed from the sand to reach 0.45 ppm.

Garf · Apr 8, 2023

Dan_P said:
Based on the aquarium data, 20 mg of PO4 was removed. From the desorption data 2.4 mg of PO4 was desorbed from the sand.

You are correct that the sand reached equilibrium, but that does not mean the PO4 was completely removed, as you found out. Rather, the desorption stopped when the concentration reached 0.45 ppm. If the volume of water had been larger, more PO4 would have desorbed from the sand to reach 0.45 ppm.

Thanks,Yes, the second round of desorption topped out at about 0.4ppm in the water, so about 10% less than the first round. Onto round 3 now

jda · Apr 8, 2023

Dan_P said:
If the volume of water had been larger, more PO4 would have desorbed from the sand to reach 0.45 ppm.

...or the water level would have went lower to reach a different equilibrium with the larger water volume. I know that you likely meant this, but wanted to clarify for other readers.

All of this is commensurate with the past stuff that shows exponential binding.

Dan_P · Apr 8, 2023

jda said:
...or the water level would have went lower to reach a different equilibrium with the larger water volume. I know that you likely meant this, but wanted to clarify for other readers.

All of this is commensurate with the past stuff that shows exponential binding.

Good catch!

Garf · Apr 15, 2023

Garf said:
Thanks,Yes, the second round of desorption topped out at about 0.4ppm in the water, so about 10% less than the first round. Onto round 3 now

Third round topped out at 0.3 ppm (Hanna), onto round 4