I would wait until your ammonia level is nearer to 1.0ppm ( just don't let it exceed 1.0ppm for a long period of time) but doing a PWC(partial water change)when it gets to .75ppm is OK. I would use new water that is conditioned with Prime rather then adding it to the tank directly. It is safe to add it directly, and to double dose if neccessary. You can use up to 5 times the dose needed if the levels are becoming toxic. The reason why it takes longer in your case is because you are monitoring the ammonia. The trick is to maintain the ammonia under 1.0ppm, but don't remove all of it. Prime only detoxifies ammonia, the PWCs remove it. You want traceable ammonia at this point until nitrites are detectable and ammonia is not detectable without doing any PWCs. The hard part is you need the ammonia because it is the bacterias food source. No food source, no bacteria. This takes alot longer then if you didn't let the ammonia build, but it is better then sick or dead fish? Most people new to the hobby do not want to deal with sick or dead fish. If it doesn't bother you replacing them if they die or get ill, then let the ammonia build until nature does it's job and the first stage of bacteria grow. It will be quicker this way for sure. Prime shouldn't lower pH, but if it does, use a dash (1/8 tsp) of baking soda and check pH after 2 hours, repeat until pH is above 6.6ppm pH. If it doesn't dive below 6.6 that is fine. Lower pH water with ammonia is actually less toxic then water that has a higher pH. Here is a link to Seachems website and article about Prime.

Here is a link that might be useful: Prime

I know what you are saying, but I don't want the fish to be harmed. At least, I want to do all I can to save them. I know that the process will take longer this way, but ....thanks...the article was very helpful...I have posted other messages with different info.....please advice..thanks!