I used all fresh water and declorinated it. I used the same sand, decor, and plants. The ammonia is a tad high reading .5ppm. I just put in some ammonia lock. but I think it is to late. I also tucked the old filter media from the smaller filter behind the new filter medium. Water is a bit cloudy. But I figured it was a bacteria bloom.
All of the fish I had have died excluding the Cory catfish. I had 3 labs, 2 red zebras, 2 peacocks, and 2 berivs. I am so upset and scared to buy anymore. The Cory fish are acting normal. What could have killed the Cichlids in a couple hours but the Cory's live threw it?
In that case the only thing I can think is you stirred up rotting stuff in the substrate when you moved it. If you move to a bigger tank it's probably better to cycle it before you move anything out of the small tank, and get new filters and so on. You can always use extras of those anyways. That way all you need to do is pop your fish over.
I'm so sorry for your loss!!! It is odd that the cory cat survived though.
Your DIY background could possibly be part of the problem given that you used cement though that will depend on how you constructed it and whether the cement was cured. Usually cement needs to be cured AND go through a period of rinsing to reduce the alkalinity. Could you provide more details on how you made the background, including all materials used?
I used the pink Styrofoam insulation and Door and Window 100% silicone to glue everything together. I then used a Dremel and knife to cut out the pattern I wanted and then used hydraulic cement with three coats with no tent and then one more coat with a tent color. I then let it dry and cure for 48 hours but I did not wash it with water before putting it in the tank which is I think my problem. Yesterday I filled and drained the tank five times and now the water is clear. I added my cory fish picasimus and parrot fish that survived back in today. I know that's not ideal because the tank needs to cycle again but I don't have any housing for them for that long of a Time hopefully all goes well