At the beginning of the month, I saw that my smaller anglefish's mouth appeared to be stuck open. He could not eat and the other angel began to pick on him with an alarming enthusiasm.
I moved the fish to a quarantine tank and began to do some research.
Searches of the Internet for Anglefish mouth stuck open yielded lots of hits and advice ranging from check its mouth for something stuck in it to there's no hope. I followed this up with visits to local fish stores. At one store, the fellow working the shop, not the owner, had never heard of such a thing and had little to offer. At the other, the fellow said he had seen the phenomenon and it happened more among angelfish and dwarf cichlids than other types of fish. He said they usually starve to death.
Disheartened, having raised this pair from small juveniles, I resolved to come up with a reasonable plan and at least try to improve my skills and knowledge with respect to injured and sick fish. I then remembered I had biologist friends, Lindsey and Chris, who worked with fish. I contacted Lindsey and described the problem. Though she and her husband didn't know the cause and were not familiar with the phenomenon, she did bring up the idea of using clove oil as an anesthetic to relax the fish and sent me a journal article about dosages. It's critical to get the dosage right because clove oil is also used for euthanizing fish. Additionally, Lindsey and Chris volunteered to come by and help me look in its mouth to verify nothing was stuck in its mouth or throat. Not having handled my angels out of the water or tried to do any fine work with them like peering in their throats, I welcomed the offer.
Within a couple of days I put together this plan:
- Treat with magnesium sulfate to see if relaxing muscles might help. (Magnesium sulfate can also be used to relax fish and is frequently used in cases of constipation. Not only did I have some on hand, I wasn't as worried about accidental overdose, like the clove oil.)
- If this didn't work, verify there is nothing stuck in its throat.
- If throat is clear and jaw still locked, leave alone for a few more days and see if it resolves on its own
- If it doesn't, consider euthanization so as to not starve it to death.
I shared this plan with Lindsey. And then, on a whim, though I didn't expect a response, with Cory, who owns and runs Aquarium Co-Op in Edmonds, Washington, and from whose YouTube channel I've learned some things. Surprisingly, Cory messaged me back quickly and told me the plan sounded solid.
Emboldened, I put the plan into action with one modification. Because circumstances were favorable and because I definitely wanted to have Lindsey and Chris teach me how to handle my fish correctly, I used the both the magnesium sulfate and checked the mouth and throat the same day. Unfortunately, if the fish's condition improved, I wouldn't know which treatment to credit.
We quickly caught the listless fish and secured it folded in a cloth moistened with the tank water. Under a bright light, using a sterilized tip of a small plastic zip tie, Chris and Linsey inspected its throat and declared it clear. Lindsey also gently manipulated its jaw, which offered no apparent resistance. Not finding anything definitive, we returned the fish to quarantine and tidied up. Then, peeking back into the tank, we noticed the mouth was no longer wide open. It was a small "O" shape, not quite normal, but different, at least. Chris recommended some API Stress Coat and we took a wait and see attitude.
Two days later, the fish's mouth was still slightly puckered and he hadn't shown any interest in eating and moved only to hide when I peeked in the tank. It also had an abnormal whiteness to the upper part of its mouth. I contacted Lindsey and again and she confirmed my impulse to return it to its home tank in hopes that it would reduce stress.
Back in its tank, the fish hid, but in a couple of days the mouth looked more normal and it was making half-hearted attempts towards food. In another day, I returned home late and the main lights had already gone out, leaving only the dim bluish moonlight and I put a few flakes at one end for the more aggressive angel, and then sprinkled a few above the ailing fish. To my delight, it darted to the surface and grabbed a big flake, sucking it in normally, even though its mouth still didn't look quite right.
Over the next week, the fish continued to improve, showing deepened color, ever increasing enthusiasm for food, and now 20 days later, seems completely recovered.