Blenny is a Lawnmower Blenny, aka: Jeweled Rock-skipper, Algae Blenny, and others I’m sure. We had already added a few hermit crabs and snails, but he was the first fish addition to the tank. While I will refer to him as “he” throughout, his sex is unknown to us. There are no methods by which to identify it visually.
In the wild they are found from eastern Africa to Micronesia (according to Wikipedia anyway). This information is particularly interesting to me as many species kept in captivity would never meet in the wild. While it’s easy to assume that, just because all the fish prefer similar water parameters, they come from very different ecosystems. When keeping a reef tank you’re not only trying to create an ecosystem, you’re creating an ecosystem that doesn’t exist in nature.
Blennies are frequently considered herbivores, consuming primarily green hair algae but are also detrivores, consuming detritus. When we first added Blenny he would spend most of his time biting at the glass and rocks. Lawnmower blennies don’t have teeth but rather have rasping lips which they drag across the rock or glass and consume what they scrape off; primarily algae but also debris that has landed there. He refused prepared foods but that wasn’t really an issue.
While recovering from an illness (I’ll go into that on a different post) he began accepting algae tablets. This has steadily progressed, over a period of months, to him readily eating mysis shrimp, a common food for carnivores. It was amazing watching this happen over that time period.
When he was in the quarantine tank (just him and a piece of PVC) he only had access to the algae tablets. The first time I saw that a piece of algae tablet had gone missing, it was an accomplishment. As was when he began chasing them when he couldn’t see me, then when he could, then as I was adding them. It was always several days between each of these milestones, so it always felt like a different small victory. Fish are naturally cautious; you don’t get to be a big fish if you pretend to be a bigger fish than you are, but they do learn over time.
Nowadays he’s always the first one to the glass when he sees me preparing to feed them. He seems to prefer the shrimp above all else and will race the cardinalfish to get it. His mouth is not meant for this sort of behavior so he’s quite clumsy about it. He does know how to throw his weight around though.
Since the start of his recovery he has been getting increasingly territorial with regards to anyone competing in his area, which is the front right corner. This is primarily the inverts (invertebrates, i.e. snails and hermit crabs) but also, occasionally, another fish. He has engaged in some remarkably vindictive behavior that we have seen.
He’ll frequently pull astrea snails off of rocks, or flip them over when they are on the sand. This is especially bad for astreas, as they are incapable of righting themselves when on their back. This leaves them open to predation, which many tank-mates will happily engage in. I’ve even watched him pick up a nassarius snail, who was too close for comfort, with his mouth and carry it to the other side of the tank.
I have much more to say about his behavior, I’ve only touched on some of it here but this post is long enough already.