Word to the wise; for anyone considering using PlantGro in the future:
I cannot find anything on the bottle or anywhere on your Web site that tells me how often one should put this product into the aquarium.
You should test the iron level in the water on a regular basis. Plant Gro should only be added when you have seen a decrease in iron level of the aquarium.
The Nutrafin Iron Test Kit is the best tool to tell when an additional dose is required by the plants. The iron level has to be maintained between 0.25 to 0.5 mg/L. Weekly dosage without ensuring the iron level has dropped may be, in some cases, too much. Especially if the tank is not really planted heavily enough to use the available iron in the weekly period.