Does sera phosvec bind phosphates permanently, or can they get back in solution in the aquarium?
I have been running a well stocked (approximately 1 cm/liter fish, based on 250 liters) 300 liter tank. I change about 25 % of the water every fortnight.
due to the high stock the water changes should rather be carried out weekly!
I have been dosing approximately 30 ml sera phosvec twice weekly right before the filter intake for about 6 weeks. Hardly any visible phosphate precipitations occur in the tank, although the phosphate levels do not exceed the desired < 0.5 mg/l range. I suppose the phosphate precipitation takes place directly in the filter, and the phosphate precipitations are trapped in the filter.
This is very likely, as the liquid sera phosvec is immediately drawn into the filter with this addition method, where it reacts with dissolved phosphates!
Do the phosphates remain bound in the filter for a longer time?
Yes, the phosphates are permanently bound.
Is there a risk that they are partially re-dissolved?
No, getting them back in solution is possible only with concentrated mineral acids (e.g. sulfuric acid), but not under aquarium conditions.
Dr. Bodo Schnell