Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
I am not familiar with the fertilizer product line you are using.
The goal is to provide the nutrients the plants need in something close to the amounts they need. A low tech tank will not generally need as much fertilizer as a high tech tank.
A tank with lots of fish food added will not need as much fertilizer as a tank that has fewer fish, and therefore less fish food.
Root tablets or Osmocote are good ways to fertilize plants that grow roots into the substrate. They do not fertilize plants that are usually grown attached to driftwood or rocks, and do not fertilize floating plants. If you disturb the substrate then these fertilizers can end up in the water.
The fertilizers that you add to the water (including fish food) will fertilize the plants without roots in the substrate.
Given that your NO3 is staying high, I would not add any nitrogen fertilizer.
If the NO3 is from fish food, then I would assume the fish food is also supplying phosphorus and trace minerals. Fish food tends to be low in potassium and iron.
In starting to fertilize this tank I would use potassium, iron and carbon such as Excel or DIY yeast/sugar CO2 source. While many plants can use the carbon from carbonates, not all can, and even those plants that can do this have to expend some energy to do it. Better if they can get their carbon in an easier way.