I had to purchase a larger filter for my 10g tank with 3 goldies (yes, I know--overstocked). So I am well aware that the tank will need to "re-cycle". However, the ammonia level has been at 4.0 for the past 6 days (since adding the new filter--an Aquaclear 30). Is there anything I can do to bring the levels down to a safe level? I have been doing daily 25% water changes, to no avail. I've added ammo-lock and stress zyme. I've has also only been feeding the fish very small amounts of food, every two days. Any thoughts??

Your test kit is probably reading the bound ammonia if you are using an ammonia binder. It is there but is rendered harmless too the fish.
If you can please answer a few questions;
Do you have a heater?
What is the ph and kh(total alkalinity)?
How are the fish behaving? Anything out of the norm?

an overloaded tank tends to have this problem.. especially if it is not cycled..

you may need to interfere by remove the excessive debris or uneaten food manual and frequently.. and replace water only with treated water or water the left sat overnight.. when changing water, jus make sure ammonia is brought down to 1.. for u still need a bit of ammonia for the require bacteria to develop..

add some salt to stablise the tank.. about half a teaspoon per gallon of water is sufficient... no need chemical as this may affect cycling process..

reduce feeding amount (reduce by 3/4 of normal feeding amount) and continue to feed on daily basis instead of feeding massive/normal amount on alternative days... right now you are more concern about tank cycle instead of whether the fish is hungry or not.. better off to be hungry than living dangerously in an uncycled tank...

cheers

Thank you for your response. The pH level reads 7.0 and the alkalinity is quite low, only 40. I do not have a heater on the tank, and water temp is 72 degrees. The fish seem to be acting as usual. I haven't seen them gasping at the top of the tank. I have a black moor that has always kind of "hung around" the tank, a slow mover I guess.

I checked the ammonia level today, and it has decreased to 2.0. Another question...should there be nitrates rendering on the chemistry tests? Because they are registering at 20ppm at this point??

What are your tap water readings??? (I ask only because my tap water comes with 20ppm NItrAtes and .25 ammonia)

Have you been getting any nitrIte readings???

Jenn

The reason I asked those questions is because they will all play a part in your cycle.
Nitrifying bacteria do better with a warmer temperature. Seventy two is not too bad but 78-80 would be better. Heaters are cheap and IMO are a must on a goldie tank, especially a ten gallon.
The bacteria also does better in a higher ph environment. Again, 7.0 is not too bad but a little higher would be better.
There also neads too be sufficient alkalinity for them. So here we go again, 40 ppm is low but is sufficient. Ultimately I would get that higher with some baking soda but for now just leave it be. Once you read zero ammonia it would be a good idea too up the kh then.
I would add some FISH SAFE salt at the rate of 1.5 teaspoons per gallon. Dissolve it first and then pour it in the tank away from the filter intake. This will help with your nitrites that you will inevitably have now since your ammonia is declining.
Keep up the small partial water changes and replace whatever salt you remove. For instance, if you remove one gallon of water add only 1.5 teaspoons of salt with that water change.
Once you are reading zero for ammonia, and NITRITES stop using the salt and you could start feeding a bit more. Just don't go nuts. Then you can relax a bit and enjoy the tank.