[rjordan393]

Hello, I am trying to understand the chemistry of my fresh water aquarium with plants.
        If a plant nutrient such as nitrate, phosphate, potassium and etc  loses or uses up its anions or cations, then are these nutrients still usable by the plant?
What needs to happen for a nutrient to lose or use up its cation or anion?

If these nutrients lose their charge, will they still show up in a test?

I do not have a chemistry background and I hope my questions make sense.
   

[Borek]

All nutrients are absorbed when dissolved, in case of salts that means they are dissociated - so the cations and anions are separated (but both still there in the solution).

It doesn't mean they "lost their charge". During dissociation neutral molecules split into charged ones. The solutions stays neutral overall, as the amount of positive charge in cations and the amount of negative charge in anions are identical.

Typical tests require the nutrient to be dissolved and dissociated (in either forms of anions or cations), so yes - they will show up.

[Zyklonb]

Right, a cation is a positively charged ion, they are metal ions like potassium, aluminum or calcium. An anion is negatively charged, and is almost always non-metals like chloride, oxide or sulfide or they can be poly atomic like nitrate, sulfate or phosphate.
These ions are very stable as they are, and cannot easily loses there charge. For example, if a potassium ion gained an electron, it would make potassium metal, a very reactive substance which would quickly ditch the electron again if it can.
These ions won't lose their charge.