[Deanna]

I’ve watched a bunch of different videos by this author and have struggled to agree with most, if not all, of his conclusions. I suspect that it is due to a limited sampling that is being studied and, by coincidence, the tanks(s) used just happen to respond well to the conclusions. It’s called curve fitting. He seems to have magic solutions (P is a trace element??!!) that contradict, at least, what my understanding and anecdotal experience allows.

If his conclusions were correct, would I have major BBA problems if my PO4 levels were persistently in the 5ppm area? I keep my PO4 levels in this area, far above his recommendation, yet I have no BBA. So, I think it is more complex than just saying low PO4 = low BBA. In a planted tank, there are probably other variables, e.g.; ratios to NO3, pH, etc, that are involved. In a non-planted or saltwater tank, then I agree that PO4 is a significant algae inducer.

 

[Deanna]

I'm going to suggest a possible reason that this particular old wives' tale has some merit, but it is not applicable to dosed PO4. PO4 is the orthophosphate (inorganic phosphate) that plants use. If we don't dose PO4, the vast majority of the phosphate in our tanks is organic phosphate from the waste stream, and this cannot be measured by our phosphate test kits. As the name indicates, this is an organic.

So, if we have a high PO4 reading, and it is not the result of intentional PO4 dosing, this means that there is a very high level of unmeasurable organic phosphate and, therefore, general organics (waste) in our tanks and we do know that high organics cause algae to proliferate. It may be that, without realizing it, what used to be perceived as the enemy (a high PO4 reading), was actually just a proxy for the total organics, which is the true enemy.

If true, this lets everyone off the hook, but does point to the need to separate dosed PO4 from waste-sourced PO4. In any case, it still makes no sense to remove PO4 from our tanks but, as a proxy, will show that we need to remove/prevent the organics (waste) package.

 

[Deanna]

This is a good point.

IMO, there is a difference between nutrients generated from tank neglect than those from dosing.

If you recall, we have had this discussion a few times over the years.

It has to do with the manner in which it was generated. In general, if NO3/PO4 is high because of lack of water changes and poor maintenance, that is recipe for BBA and many other algae. But in my experience, an uber clean tank that is dosed to high level of ferts is completely different.

Yes, but I still maintain that an ionic compound is an ionic compound, e.g.; NO3, no matter the source is identical to NO3 from any other source. It can’t be different, other than the way in which it was created. However, I agree that high NO3, PO4, NH3/NH4 readings (the only things in the waste stream that we can measure with our hobby-grade testing) that are not the result of dosing, do indicate an overall detrimental waste problem. In this case, algae won’t be the only problem.

If I could, I would eliminate all nitrogenous and phosphorus sources in the tank, other than what I dose. This would mean an ultra-clean environment, unfortunately it would also have to be a sterile environment.