If your filter inserts are green it indicates a water born algae. Could
your filter be filtering out GW?

Give us your filter cleaning routine also..... A high level of nitrates
could indicate decayed matter under the UG plates. Exact parameter
values may be very helpful. You may not get much satisfaction from
products to clear water or algae....... If the water is milky-white
cloudy it may indicate a bio colony problem. If it's green cloudy, it
affirms the GW. As far as the ammonia..... it's apparently the most
toxic of parameters and a sharp spike in ammonia levels may have gone
unnoticed by your tests but cause a big problem in the fish.

I don't know just how many plants you removed, but reintroducing them
might soften the problems with your tank. Plants injest many substances
harmful to fish..... Something else to consider is: when removing the
plants you disturb the substrate possibly releasing tons of trapped
stuff into the water...... I know that from experience. If your lucky
it only results in increased algae.

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