I have had my ten-gallon tank for at least 2 weeks and before that, I only had a 2.2 betta tank (small I know). I thought I would kick-start the cycle by putting in dirty filter water into my tank as well as tossing in some fish pellets. After about a week the water parameters read 0 Ammonia, 0 Nitrite, and 2.5 Nitrate. I got excited and put in 2 baby platies (a friend had too many). The next day I figured the platies were doing great so I went to get 3 guppies (2 female) and 2 African Dwarf Frogs. I noticed two days ago one of the females was acting very weird: not eating, moving to stay under filter flow. I tested my water each day and ammonia was a tad high, but never above .25 ppm. I figured I would do frequent water changes to counteract the Ammonia/ Nitrite. Sadly, I found her dead the next morning, thinking it was swim blatter disease I removed her. I then noticed the guppies had red gills and I then removed my betta from the 2.2 gal and cupped him for the night. I placed all the fish and frogs into his tank due to it being very well cycled with similar PH and Temp. Now my betta needs his home back, the fish living there are cramped and their old tank is deadly. I did a 90% water change once they were all out. What should I do, my other guppies seemed very odd and are showing red flag signs of ammonia poisoning (the male has a red streak on his body, the gills on the female were turning red), the baby platies and frogs are harder to tell. I plan to go get some aquarium salt and maybe bacteria booster and try to treat the guppies in their old tank. Then eventually get them all back. I'm new to the hobby so I apologize for the super long post I just wanted to get all the info and my thought out there.