Dying Older Cichlid

Question
I have a 7yr old zebra cichlid that has been very hardy unitl recently. As of now he is on the bottom of the tank breathing slowly and I'm afraid he is dying. Besides age the only thing that has changed was a thourough cleansing of the tank of about 75% of the water with a deep gravel clean.  Addition of a small blue lobster and lighting change to a blue light.  Any ideas?

Answer
Hi Christian
It could be due to the large water change, especially if there was any major ph difference or if the nitrates were really high before(old tank syndrome) and he was used to that, or even if there was a temperature change in the water, it might've been enough of a change to shock him.  

Be careful with the lobster in there, especially if the fish is just sitting on the bottom.  Lobster's can be aggressive and go after the fish.

Just give him some time, probably leave the light off and hopefully he'll pull through ok.

Christy