View Full Version : Cooking rock (Phosphates) help

07/19/2018, 08:47 AM
I have rock that came out of a high phosphate tank. I've been "cooking" it in a 50g vat and a 5 gallon bucket, with DI water. The bucket I'm changing the water 3 or 4 times a week. The vat gets a 100% water change once every week or two. I'm testing phosphates with a Salifert test. They are staying steady at 0.25 to 0.5. Source water tests 0.0 so I believe that the test kit is good.

Any Idea how long I should expect to have to keep this up? Any suggestions?

07/19/2018, 09:04 AM
All the organics are done decomposing. Ammonia, Nitrite, and Nitrate are all testing 0 now.
I'm not interested in doing the acid bath.

07/19/2018, 02:11 PM
The decomposition may be complete or the rock may have cycled well enough to handle the nitrogen compounds still being created.

If you continue on your path of exporting the phosphate with water changes, the phosphates will someday be exhausted. It may be quite a while however. I would suggest you try Lanthanum Chloride to speed the process. That may require that you use salt water rather than fresh though I'm not sure. It still may take a few weeks to exhaust the phosphate. You might also ghost feed to keep the cycle going while the phosphates are treated.

07/19/2018, 04:24 PM
I agree with using lanthanum chloride (SeaKlear, etc) to precipitate the phosphate. The number of water changes required might be huge if that's all that you do to remove phosphate. Ammonia, nitrite, and nitrate can be converted to nitrogen gas over time, and leave the tank in that form. Phosphate can't outgas, so it takes more to remove it.

07/20/2018, 01:20 PM
Ok, Thank you. I'll look into lanthanum