if your tank is spiking do a waterchange as soon as you can. raise your water temp slowly to 83 add a tablespoon of salt per 10 gallons. Continue water changes daily . If the ammonia is spiking you should be doing at least 50 % every day. If you can get some seachem stability and seachem prime use those two items. Does the stability straight into your filter everytime you do a water change for a week. Prime your tank every 24 hours it will help with the spikes. But keep on those water changes everyday because ammonia is very bad for Dempsey's . The stability will help re establish your beneficial bacteria. Try not to feed your fish everyday so it keeps your water in check. Only once every three days. and make sure you only throw one or two pellets in at a time to make sure they consume them .