Read the exact product label
Fertilizers vary by formulation and dose. Do not assume that a product marketed for aquariums is automatically safe for every shrimp setup or that a trace ingredient is harmless at any concentration.
Check the label for invertebrate guidance and use the stated dose for your water volume. Do not combine several products without understanding their overlapping nutrients.
Observe and test
Dose carefully and watch plant and shrimp behavior. If an issue follows a new product, stop adding it and test water before taking further action.
Avoid hobby claims about a universal safe copper concentration. Risk depends on chemical form, water conditions, exposure, and the animals; seek manufacturer or qualified guidance.
For your own tank
Dose for the actual water volume and do not combine products casually. Save the package and note when the fertilizer was added if shrimp behavior changes. If a label does not address invertebrates, ask the manufacturer instead of trusting a universal safety claim.
Use these as general hobby references. Test your aquarium and confirm product guidance before making changes.