Have some fertlizer here, wondering if it is safe...

Sounds OK for fish, but are you really sure you want to add nitrogen and phosphates to your tanks?

There is no need to do a double post. Pick one area and post your question there.

The stuff looks ok to be added to a fish tank w/o harming the fish.

-Richer

What are nitrate and phosphate readings in your tank water?

You have to understand, that those are added only if you have a real shortage of them. Otherwise, you're risking to get severe problems with algae.

In real life, nitrates may need to be supplemented in densely planted and actively growing tanks with low fish load. Additions of phosphates are needed extremely rarely (and, mostly, in plants-only tanks). Both, nitrogen and phosphorus, are brought to the tanks with fish food, so the higher your bioload is, the less likely you'll need any additional source of nitrogen and phosphorus. Most often, we see people struggling to limit those and not add more of them.

Copper supplement, IMO, is not needed and may be dangerous in a long run for your plants and inverts. Your tap water should provide more than enough of it.

Tell us about your tank: size, age, population, plants, light, CO2 supplementation, etc.

What test kits did you use to get those results?

Richer is correct.