Why do cichlids, marine fish, and some other fish get hole-in-the-head?

[confused_aquarist]

I have heard that contributing causes can be diseases or nutrient deficiency. It occurs in fish that have intestinal protozoan infection, mycobacteriosis, or gill/skin flukes. I have also heard of cases where camallanus worms are associated. But the pathogens (even bacteria) are not detected in the so-called holes.

Clearly, the symptom seems to be nonspecific. I’m just wondering if there is any biological reason for the sensory pits of the fish to erode. Can they be the result of secondary bacterial or viral infections? Or is this merely a biological response to expand the surface area of the sensory pits, I guess so that the fish can be more sensitive to incoming danger signals? (I guess I might be looking for more of an opinion rather than evidence, though evidence is always preferred).

 

[GaryE]

So you are asking why that specific spot on the head of the fish is 'attacked'?

I can only offer anecdotes. This disease seems to affect large fish more than small ones. I see it is as a by product of large fish in too small tanks for their needs, without enough water changing. Stress and poor conditions are triggers. I've temporarily cured it in Geophagus with twice weekly 50% water changes. But that becomes quite a task to maintain, and since Geos need large tanks, a lot of water is involved. Still, I see it as the price of keeping such creatures in captivity .If you slip, it returns.

I've seen it in smaller dwarf Cichlids when I've bred them in numbers, and not been able to sell them quickly enough. Too many males in crowded growout tanks, and it begins. The fish can't ever be distributed. It tells you the fish are being poorly kept in too small quarters with unclean water and high levels of stress. That part is hard to admit to, but doesn't answer what the pathogen (s) is or are.

The consensus is it's usually bacterial. Many of the wounds have been swabbed and analyzed. I suspect it isn't just one pathogen, but there are multiple causes.

I've seen but not saved papers on the pathogens found, and someone will likely provide some. They look at the pathogens in isolation. The element they lack is the observation that this disease is triggered by aquarists not working hard enough. It begs the question of why we keep fish whose survival demands several water changes a week in tanks not suited for them. We stubbornly look for the right antibiotic when our choices cause this one. A hobby isn't supposed to be work, but we go there far too often, and our pet fish pay for it.

 

[Rusty_Shackleford]

Many cichlids kept in improper conditions can become susceptible to HITH. HITH is caused by Heximita living in the fishes gut.
Poor water quality/husbandry is most certainly a contributing factor as well as proper water chemistry. Put an Oscar in hard water you're bound to see HITH. Put Mbuna in soft water, HITH.

 

[Back in the fold]

Dirty water . Poor water change schedule . Big fish need big water changes and often .

 

[confused_aquarist]

I have not kept big fish, but I think they will shed very big poop. It's beyond me how the bigger poop will be processed, it must require a lot of bacteria, or maybe the tank keeper will meticulously remove them manually. Either way it seems awfully difficult! Here I am struggling to keep 0 phosphate in planted tanks with only small fish.

It is so very interesting why the symptom shows up as HITH when the real disease is actually often internal. Or maybe it's only a secondary disease like the tail or gill rot.

 

[Magnum Man]

back in the dark ages before the internet, it was rumored to be caused by a parasite, I assumed by an external parasite similar to what infects our native cold water fish during the heat of summer, which were always called “worms” though I suspect the “worms” were caused by a bacteria

 

[GaryE]

I've read analyses that say it isn't just Hexamita. But it seems a bacterial condition that persists and flares up once it's established. The key is prevention via water quality and tank management, including proper stocking.