Well,
This is your problem: you have one filter and you clean it too often. You cleaned your filter and you killed most of good bacteria, that why your Ammonia is not 0.
If you must clean filter clean only sponge, and use only cold water. I clean my Eheim 2080 once every 3-4 months, even 6 months. If the flow is OK you don't need to clean your filter.
I recommended to have 2 filters. When you clean one filter second you do not touch. Then after 1-2 months you can clean the second one, but only if you really need, when the flow is bad. Never two filters at once.
Motoro is much, much stronger stingrays than Retric. Retric are really delicate and they need really good water. I have exactly the same problem like you had. My retric do not eat, and ammonia is 0.5ppm... because after cleaning my tank, I forgot to turn on my second bio filter... and now I need to change water everyday, using Prime and testing water often. I will do it probably for the next couple days, when my bio filter will be ready.
Good luck !