There really is not a lot of reason to want to raise the ammonia levels. You only need enough bacteria to cycle what 7 small danios (you wrote Dinos which I think was a typo?) put into all that water. However, you will have to ramp up your stocking very very slowly. For example, adding another 7 danios would double the bio-load and essentially put you through a mix of fish in and fishless cyclying. To avoid this you would have to add just one or perhaps two more danios and then wait til the cycle caught up- likely from a day or two to a couple of weeks max.
Incidentally, different fish react differently to given ammonia levels. As a result it is usually suggest that one use goldies (not feeders) for cool water tank fish in cycling and zebra danios or barbs for warmer tanks.
Also, you said the filter was used. How well did you clean it before you put it on your tank? It is possible that there was dried organic waste in it which would contribute to ammonia levels once it was all back in the water. Feeding, since it become either fish poop or uneaten waste, can contribute to ammonia production as well. If the biowheels were dry for a long enough time some to all the good bacteria and the biofilm in which they lived would be unseen waste too. Finally, it is also possible that you could be getting false readings due to the dechlor brand you are using.
On the other hand you don't have to worry a ton about ammonia and nitrite levels because they should not get dangerously high for any period of time. You should monitor, but the odds are very good you won't find yourself in need of frequent large water changes here.
What most folks fail to realize is that you can not just pick a specific level of ammonia and claim it will be really bad for fish. One must factor in the influences of both pH and temperature. Ammonia is more toxic the higher the pH and temperature. So an ammonia reading of 0.2 ppm in pH 8.5 water at a temperature of 68F (20 ) would require a water change to lower the ammonia level. In the same temp tank but with a pH of 6.5, you need to get over about 15 ppm before needing a water change. In the same two tanks pH wise, if you raise the temperature to 77F (25C) the ppm levels where you need to change water drop 0.1 and and 11.1 respectively. Here is why:
The exact concentration at which ammonia becomes toxic to fish varies among species; some are more tolerant than others. In addition, other factors like water temperature and chemistry play a significant role. For example, ammonia (NH[sub]3[/sub]) continually changes to ammonium (NH[sub]4[/sub][sup]+[/sup]) and vice versa, with the relative concentrations of each depending on the water's temperature and pH. Ammonia is extremely toxic; ammonium is relatively harmless. At higher temperatures and pH, more of the nitrogen is in the toxic ammonia form than at lower pH.
From
http
/fins.actwin.com/aquariafaq.html
For those of you who get fish shipped in, bear the above in mind when you are deciding how to acclimate the fish. If you raise the pH and/or temperature of the water, you may be unwittingly raising the ammonia toxicity.
Also, Water, why do you need an RO unit?
Fisless cycling is useless here unless the OP moves the fish out of the tank.
