Not good.

[SkwidsLair]

I've been discussing the health of my YoYo loach in another thread in the disease section (link in my sig). I did some water testing, and as it turns out my nitrites are fine...but my amonia is up to 3.0mg/l.

That is so not cool.

And this is just after I've done a 25% water change, all fish are accounted for and I've added four amazon swords.

So now...I know I have to do another water change. The question is, how much of one should I do?

 

[noncentric]

You should probably do as many water changes as necessary to get the ammonia down at least below 1.0 - maybe a couple 50% water changes will be enough. Water changes can only hurt if the "new" water has a very different pH, kH, or temperature than the "old" water.

I see you decided to go with live plants. Good choice.
The amazon swords probably won't make a noticeable difference on your ammonia and nitrite levels, since the swords are usually slow-growers. To really hit the ammonia/nitrites, then fast-growing stem plants are best (something like anacharis or hornwort).

Good luck!