The Clown Loach has many unique characteristics beginning with its morphology. They have a column below each eye that becomes erect when they are stressed in any way. They may use it to defend themselves or attack other fish, which only happens once to my knowledge because clown loaches are normally very peaceful. When you have multiple clown loaches being added to a tank, they can fight over who will be the Alpha, the top dog, so to speak. In these fights, the subocular spines are erect and some fish may sustain permanent scarring or other minor damage. When a clown loach is captured for transport, they will usually erect their subocular spine. At this point, you need to be careful not to get stabbed with your spine when handling the fish. Also, if you are using a net, the backbone can easily get caught and possibly cause serious injury to the Clown Loach. Another consideration of the spine is that if you put the clown in a bag to transport it, you can break the bag with the spine. Therefore, it is better to double or triple bag them, or even better, transport them in a solid container. You can also see the upright spine when the clown shares a tank with more aggressive fish species.
Docile Clown Loaches are easily frightened, so it is recommended to have other peaceful species to share an aquarium with. Sometimes the spine can remain upright for more than 12 hours after an encounter, it will eventually return to the resting position. One thing you may notice when looking closely at a clown loach is that it does not appear to have scales. Even if you don’t believe everything you see. They have very small, faint scales on their bodies, but none on their heads. They also do not have fur covering their eyes.
Another curious thing that you will notice is the clicking sound that clown loaches make when they eat or fight. It can get quite noisy, so loud, in fact, that you might be fooled into thinking the tank has cracked. They make the click by grinding the pharyngeal teeth. Imagine if you were sitting by a river bed in Borneo (where clown loaches live) and you started to hear them snapping; thousands of them by clicking. I think it must be as strong as many frogs in a pond, but I digress.
During late spring, you may notice strange behavior from your loaches around dinner time. Well, you can always expect strange behavior from them, but this behavior only happens once a year for a short period of time or it may not happen at all. Some aquarists find that their clown loaches have “feeding frenzies” in late spring. They all attack the food as if they haven’t been fed in weeks. I speculate that they do this for something in their natural habitat. It could be a time when food is scarce for them in the wild or maybe they need to get as much food as possible for the breeding season.
In the interest of keeping this article short, I’ve limited the unique attributes to just a few, but if you have a Clown Loach, you know there are many more.