I removed the under-gravel filter that is in my 55 gallon fish tank. I've never used this filter before, even though I believe it may have been used by the previous owner. After I removed it, I immediately cleaned all the muck that remained from the filter(I took out one filter plate yesterday and I took out the other one today). I also cleaned the rest of the gravel since my tank was due for a small water change. Then,I replaced all the water that was removed. Before I did all of this I moved both my Tiger Oscar and my Achara Catfish to my 35-45 gallon tank(this tank is cycled and running good so I know it's fine). Now planning to move them back to the original 55 gallon tank. I really don't know when I can put them back into the 55 because I have no way of checking for ammonia,pH, nitrates, nitrites, etc... So I just need to know if I can put them back into the tank without killing or hurting them. Any help would honestly be appreciated! Thank-you!