Today during water change notice Java fern at the end of 4 in pvc pipe where my Irwinni head was so reached in and it started making a vibrating growling sound. It was very freaky lol
It likely felt threatened, it's normal for cats to do that, they scrape the end of the pectoral spine on the inside of them against something (I don't remember clearly) and it causes vibrations and a noise
When I had my two 4 lines I'd always hear them growl at each other in the middle of the night while their feeding or attempting to take the log from my old sun cat
If I'm not mistaken its a bone plate at the end of the pectoral fin and they'll click about when threatened or upset
Why are they referred to as "Talking Catfishes" I hear you ask? I will now attempt to answer this question. Doradids have two ways in which they can produce "Talking Sounds", which subsequently gives them their common name. The first way of communicating sound is by the fish partially locking their pectoral fins in their sockets, and then the action of moving the fins, the fin spines grate against the socket producing the sound. The second way, in which these fish produce sound is via a mechanism known as the "elastic spring mechanism", there is a muscle that is attached to the rear of the fishes skull at one end and to the anterior of the swimbladder at the other end. The fish is able to quickly contract and relax this muscle and as a result it can make its air filled swimbladder resonate to produce sound. These catfish use these methods of communication as a means of self-defence against would be predators and also as a way in which they can find conspecifics in its natural environment (or aquarium)...
Got two of them as well and they are "talking" quite often, especially during the night. Got so bad i removed them and put them into the tank at my parents, because i sleep in the same room where my tank is located. It's quite impressive, they get so loud you can hear them even downstairs. Right now they are around 20 cm / 8" i wonder how loud this will get when they are twice thi size ....