Backyard Aquaponics
A place to discuss aquaponics

Try downloading the free magazine, there's a heap of information there about the nitrogen cycle.

http://www.backyardaquaponics.com/magaz ... Issue1.pdf

These questions are central to the success of aquaira, aquaculture and aquaponics Queen Megan...

Please read the article the EB mentioned, consult the FAQ section of the forum and research the nitrogen cycle throughly before you commit to stocking any fish....

You'll find loads of info on aquarium and/or koi sites.... as well as here....

I fear these questions may be for a system that does already have fish in it.
Please do read the info the guys pointed you to, you need it.
Here is a very quick nutshell
Ammonia that comes from fish waste and fish food gets converted by bacteria into nitrite which then will get converted by bacteria into Nitrate (that is at least what happens once the system is "cycled") as the magazine will tell, salt can help some but if your nitrite is very far above 1, you should be doing partial water changes like probably 50% until you get the nitrite down to 1 from where some salt and the bacteria cycling should hopefully catch up. Don't FEED till the nitrite gets below 1 or even lower.

I believe nitrite interferes with respiration.