Hanna PO4 testing

[Delphinus]

Originally Posted by Aquattro

Cool!! How did you manage that? You've been fighting it for years

I finally added GFO,it's made a huge difference. I still see the PO4 struggling to come back but I'm changing the GFO out weekly (Brett does the same with his). Just a cup and a bit per week (well below the recommended amounts, but well above the recommended changeout period). The nice thing is that by using the Hanna tester I can tell when the GFO is spent, and that way I know I'm not wasting GFO (stuff's expensive) by changing it out weekly.

I still have the zeo going for now, but I like that I don't need to do it as much. For whatever reason the zeo was not touching PO4 in my tank. I see sort of two possibilities for this:

1) Zeo doesn't do as much for PO4 as we might think, maybe there is a problem of scale (ie., my system is closer to 400g total, but I had great results with zeo alone when the system was more like 120g total), or,

2) NO3 was reading zero for me for a long time, maybe PO4 reduction can only occur at the same time as NO3 reduction (I think it's been theorized that NP pellets work in this manner) so basically NO3 is the limiting variable, once it cannot be reduced any further, no PO4 reduction can occur.

.. just my thoughts anyhow.

PS. I also switched to 50g weekly changes, from 24g weekly changes, and this has also yielded positive results. It was apparent within 2 waterchanges that this was a good move.