Ammonia problem

[fish 4 life]

Hey so i have had my 20 gallon tank for 2 months now and i have been having problems with my ammonia.. After two weeks i thought my tank was cycled so i got a F8 puffer.. 2 weeks later the puffer died from the high ammonia... I tested my tap water to find out that it has 1.00 ppm ammonia!!! So i then i decided to drain my tank and refill it with reverse osmosis water.. My tank was showing good water levels so i bought two pangasius cats.. with in a week my ammonia shot up and killed both fish... I have 5 neon tetras in the tank right now to help with the bacteria growth.. What do you guys think i should do? I was wondering if it had anything to do with the water i used.. This is their i get my water from.. What do you think is going wrong? How often should i change the water? I use to change 25% a week should i do more? Less?

 

[anarekist]

you might want to add some sort of trace minerals to your water, reverse osmosis water is dead water, not enough trace minerals for your fish, some marine salt maybe? i duno how much.

what kind of filter are you running? what ever it is you might want to wait a lil longer before adding new fish.

 

[fish 4 life]

I have a 50 gallon Aqua clear filter. It is 300 gph and in it i have a sponge, filter floss, and bio media... Yeah i was thinking about adding salt but i am using fine salt that is used for cichlid tanks so it has high ph.. My tank right now is 8.0 ph so on the high side and thats with no salt added.....