[Betta132]

Lately, I've seen something a bit odd. My angelfish will slowly approach one of my sunfish, and the sunfish will respond by tilting itself head-down and going pale. The angelfish will then closely inspect the sunfish's flank, and after a moment of inspection it will either lightly nip at one spot or leave without doing anything.
The posture and pale coloration looks like what's displayed by fish at a cleaner station, and the angel's behavior doesn't seem aggressive- no flaring, no posturing, just an inspection and then maybe one little nip. Could this be a couple different species worth of intimidation attempts that are getting cross-wired and look like cleaner behavior when combined, or is there any this is actual cleaner behavior?
The angel is little, if that makes a difference- under 3" long including the tail.

 

[WaterLife]

I am not entirely sure where freshwater Sunfish are typically from, but I think they may just be in North America? Where as freshwater Angelfish are from South America/Amazon, so the two species wouldn't encounter each other in the wild so I doubt they would have developed a symbiotic relationship as that of a cleaner fish.

As far as I know, cleaning symbiosis is almost entirely only seen in saltwater, with just maybe a few mentioned ever happening among freshwater fish, so the odds of it being a actual cleaning are pretty unlikely, it probably just looked that way from the peck, but wasn't actual cleaning.

However, no one can say for a fact that it couldn't develop just because it doesn't happen in nature, but it would still be extremely rare.

I haven't seen the behavior myself so I can't form my own interpretation of the behavior you witnessed.

If you could capture it on video that would be great!

But seeing as how they are probably both rather a decent size, I doubt the angel is really small enough to pick/clean anything off the sunfish and I don't think there is anything on the sunfish for any fish to pick at.

I am leaning toward it being a very submissive sunfish and the angel, wasn't intentionally challenging (so the typical domination behaviors weren't seen) the sunfish, but then just did a slight nudge/mouth push/peck just as a little reminder of who is the dominant one (guess you could call it low intensity dominating). Which is seen in many animals and even fish, where the alpha, not actively challenging, but if someone submissive crossed it's path/got in the way, it may give it a slight nudge. Or a very similar behavior, pretty much bullying, where a submissive fish would submit and stay still, but the aggressor fish would still come over just to push around the fish even though it submitted (yeah they may hover there for bit before giving a slight peck). That's been seen in many fish as well (German rams as an example, can often do this). If the angel does dominate the sunfish at other times, then there is a high chance that may be the case.

But if they both swim around peacefully never trying to dominate each other, it may just be a mere friendly social interaction/greeting between the two, maybe out of boredom/loneliness. It would be great if they are getting along, as I've heard Sunfish and Cichlids don't always work out (depending on species).

I'm merely guessing though.

Aren't they rather newly introduced together? (I don't recall an angel being with the sunfish(s))


By the way, how have the fish been doing (the one that was skinny and not doing too well)?

 

[Betta132]

I suppose it could be just that the warmouth doesn't think dominating the angel is worth the trouble. He'll chase the longear, so he's not submissive, but I guess he might just not care too much since the angel doesn't look anything like a sunfish. He could just be saying "Ugh fine I'm not boss just go away" and waiting for the angel to leave.

I don't think it's cleaning behavior, there's no reason it would develop, that's just what it looks like.

The angel has definitely been trying to claim a spot as the boss, it's just not quite able to. The longear is almost four times its bulk and, although not terribly mean, is stubborn and does not want to give up its spot. Its stance might be a gesture of "No I am not backing down" that the angel is interpreting as submissive, I suppose- they don't seem to have quite the same methods of communication. The angel postures with its fins and darts around when trying to be dominant, the longear postures with colors and holding its ground in its favorite spot, and the warmouth kinda just doesn't care unless someone tries to steal his cave.
I'll try to get a video, but every time I get anywhere near them, the warmouth starts begging for food and the angel just stares at me. I've been watching most of this in the mirrored door of my wardrobe, but I can't film it that way.

The angel was added about two months ago. He was an experimental addition, and so far things seem to be going fairly well. There's still a little bit of posturing, plus whatever this is, but I think that might be due to the fact that the angel is maturing and its position in the hierarchy hasn't yet balanced with its new boldness.
The silver dollars were a bit of a problem at first- they thought the angel's fins were edible. They figured out after a little bit that he wasn't, but he lost the tips of all his fins. I've been closely monitoring his fin length by tracking the number of stripes of each color that are intact, he hasn't lost any fin since a week or so after introduction, and they're regrowing. No further problems on the fin-nibbling front, probably because he just didn't taste all that interesting.

I treated the warmouth with a couple rounds of PraziPro for internal parasites, but he still wouldn't eat afterwards, and he got very thin. I ended up separating him and surrounding him with a lot of live ghost shrimp, and he eventually started eating them. He's still a bit underweight but is doing well, and he's very enthusiastic about food and gladly accepting frozen. He should be fine.

 

[Bushkill]

If I knew more about the reproductive and rearing habits of sunfish, maybe it ties into this:

There are several species of cichlids (and lots of other species) where parents will guard a new brood. Some species will take parenting to a higher level and also provide a first food: The slime coat produced by Discus obviously comes to mind first.

Parent-reared angelfish will display much the same behavior in our small aquariums. At pea size they will begin to peck at the parents' slime coat. Unfortunately, angelfish just aren't built to do that. In nature they would be scattered by that point. But in an aquarium, they will continue and the parents will tolerate it if they are determined parent-raisers.....to the point where the parents look tattered and shredded if they aren't separated.

Another pure guess here is that two flat-bodied fish from totally different parts of the world are simply exhibiting similar behavioral characteristics?

But I have to ask: is this a sunfish as in the ones native to most US ponds and lakes?

 

[Nordic]

Don't those sunfish poop a lot?
I tried keeping bluegill as a child, I remember how big their droppings were.

They are a pretty common invasive fish here, it always struck me how many colour variations they have according to the colour and parameters of the water.

 

[Betta132]

I think I've figured this out.
When confronted with aggression that it doesn't want to deal with, the warmouth goes head-down and fades slightly in a gesture of submission. The angel constantly has its fins out in what must look like an aggressive display to the others, even though it's just how angels swim. When the warmouth fades, a bunch of darker little spots show up, and the angel evidently wants to know if those spots are edible. It's basically culture clash, they're both misreading each other's intent. I don't think they need to be separated, the warmouth doesn't appear to care and isn't being injured at all.