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My JBJ nano cube has a 100% Florabase substrate (testing the product out). I have noticed that I can't get the PO4 levels in this tank higher or lower than 0.1 ppm according to three test kits --two Seachem PO4 test kits and a Red Sea Phosphate Test kit. Even after dosing 2 ppm PO4 with a test kit spoon, the aquarium registers 0.1 just 24 hours later (test kit does register higher values immediately after dosing). The same test kits are responsive to my PO4 dosing in the 20g long where I have a 100% Eco-complete substrate. Has anyone noticed this problem with Florabase?

Carlos
 

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Not sure why my response did come through the 1st time, I'll post another.

The Fe in the substrate might be such that it binds with PO4 intitally, after a few months or by the time all the active sites are filled with PO4 other anions, the tank will ease in to a more plant domianted PO4 removal rate.

Fe is added for PO4 removal in lakes, some makers might believe this is a good thing to remove from the water column and sequester in the substrate. Then plants can remove it via the roots or reduction, although this takes a lot more reductive power than is typically present in aquarium substrates except soil and peat based substrates with high OM content.
Laterite does a similar thing with PO4. But there is only a finite amount of PO4 that can be bound. As your tank/substrate ages, there should be a decline.

There's no way 2ppm is used this fast.
The 0.1ppm fraction is either test kit error(test against a known standard rather than against another cheap test kit), or Orangic PO4 that is not used by plants. Often there is a fraction around 0.1-0.2ppm that is never removed in tanks and plants cannot remove it.

Regards,
Tom Barr
 
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