Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Most fish food (and I would assume shrimp food) will supply a certain amount of N, P and micros. Not very high in K, Fe or Ca.
If you have a small shrimp population, then you may not be adding enough nutrients for the plants that way.
How is the NO3 running? If it consistently reads in the single digits, but does not hit zero, then you may not need to add N, P or most micros. I would start by adding K and Fe; and Ca if the GH is under 3 degrees.
The Flourish product line includes most of these as separate items, so you can customize the dose of each using Flourish Potassium and Flourish Iron. GH booster will add Ca, and Mg, and often adds K, so read the label.