If your nitrates are 0 it's possible your tank is still cycling. You
should probably test for ammonia and nitrites if possible. I'd do
water changes a couple of times a week until the tank has cycled or
the fish are better. Do the fish show any signs of illness, white
patches? Are they gasping or breathing heavily?

Hope that helps
Giancarlo Podio

(Heather) wrote in message . com...
I started with three very friendly goldfish and now I've got two left
that don't look good at all. I thought adding plants to the tank
while it cycled made it more stable. What's going on???
Setup is 20 gallon tall with 1 watt/gallon light, and a whisper
filter.
The plants a moneywort, carolina wort, sagitarius, amazon sword and
walmart bulbs (one of which has sprouted after 1 week)
The tank has been running for almost three weeks. I'm planning on
testing pH and nitrates tomorrow to see what's going on.
Should I remove the plants?
I also have an undergravel filter powered by a powerhead that I can
run. Should I get this running?
Thanks
Heather