High ammonia?

It should be zero. How old is the tank?

 

What size is the tank? Have you added anything new? Do you have live rock? If not what are you using for a bio filter?

I would try partial water changes before using a chemical buffer.

 

I tried to edit my comment. I am new to this hobby and have read that a partial water change is a good way to reduce amonia if it is not out of whack completely. Please wait until a seasoned member gives you advice.

 

Check your bio balls (If you are still using them), there could be build up of rotting food in them. It doesn't take much to affect a 29 gallon tank.

 

Please keep us posted. I would love to hear how you fix it so that i may learn.

 

yes do check your bioballs... if their loaded up with gunk, take them out and really dunk them around in some saltwater that you can toss out. Then restock them in the tank. do a bit larger of a water change on your biocube if your fish are exhibiting signs of rapid breathing you should probably chose to do a more 'rapid' change instead of several water changes over a week. Do a large chunk now, then in a few days retest (and keep an eye on your fish) and do another change if necessary. Make sure the dead chromis body has been removed by CUC if not then you need to physically remove it yourself.

Good Luck.

 

Her rid of the bio balls. I have the same tank