Yoyo Loach fat and acting strangely...

[prince]

My yoyo loach has been acting and looking different recently.

He appears to have gained a lot of weight recently. He isn't nearly as fat as other yoyo loaches that I have found photos of online in trying to find a solution to his problem, but he still seems slightly bloated. I've owned him for probably three-ish years now, and his diet hasn't changed recently (I feed the fish flake food and algae wafers, as advised by the aquarium shop) so I'm not sure what could be causing this- although I haven't ruled out just overeating! His movement doesn't appear to be affected, he's not swimming at odd angles and he's as active as he always has been, so I don't have reason to believe that he's suffering because of it. As there hasn't been another yoyo loach in the tank since a couple of years ago, I can't imagine it would have anything to do with pregnancy. Any ideas?

The other anomaly I've noticed is a weird behaviour: over probably the past few weeks, he's been doing this strange movement in which he'll lie on his side at the bottom of the tank, then suddenly flip upright in the water, then float back onto his side and do it again (I can't think of a better way of describing it than that). I don't think it's causing him any struggle as he doesn't appear to have difficulty navigating the tank otherwise, but I could be wrong. I wondered at first if his weight gain had caused him to no longer fit into his cave, and that this could be bothering him- he's claimed a tight hole in a rock in the tank as his home- but having seen him in there since, it can't be that. It could have something to do with the weather, as it's been a very hot, muggy, stormy summer here, but I haven't noticed any of the other fish change their behaviour.

I bought him first as a friend for another yoyo loach, who he long outlived, but he seems very social with other fish in the tank- I also have two weather loaches, two sucking loaches, three siamese algae eaters and a large common pleco, as well as a lot of guppies. He hasn't recently had any new tank mates, and the tank hasn't been redecorated, so I don't think I can blame any of this on changes in his direct environment. Not sure if this would make a difference, but context is always useful!

This could all be totally harmless (I rather hope it is), but I don't want to risk missing a sign that he's of ill health! He's very playful and brings a lot of life and fun to the tank, so I want to keep him well and happy. I have looked around online for answers as to what could be wrong, but couldn't really find anything relevant. I'd be very grateful for advice! I don't think I've missed anything out here, so if there's a solution I haven't mentioned, it probably means I haven't tried it. Thank you
I don't have pictures as they were rather difficult to take, but I'm sure I can get some if you need photos for a better idea of what's wrong. (First-time poster so I hope my formatting is alright!)

[Diana]

Look at the fish from several angles- front, back, top, and if you can figure out how, from below. Look at the place you think of as the 'fat'. Does it bulge out more on one side or the other? Is it confined to a particular part of the fish? Within the 'fat', are there lumps or anything?

Are you sure your fish is a male? Female fish can develop eggs, but not be able to release them without the trigger of a male in the tank. A fish that is fat because of being gravid will be uniformly fat (equal on both sides) and the 'fat' is just in the abdomen. It may look lumpy with the shapes of the eggs.

A fish that is overeating can get fat in a couple of ways. The liver can hold the fat, and this could cause some metabolic issues. (look up fatty liver disease). Or the fat could be distributed over more of the fish, in a uniform way, not confined to the abdomen. The whole fish would look evenly plump.

A fish with a tumor or other growth may look fat, but more often the growth is not evenly distributed. There may be more of a lump on one side, especially if the growth is close to the skin, or just under. If the growth is in the middle of the fish then the 'fat' may look more uniform when you compare the sides. The rest of the fish will not look 'fat'. A tumor or similar growth may look uneven, or lumpy. Or it might be a more smooth bump.

A fish with dropsy will not usually act healthy in other ways. The fluid may collect in the abdomen, around the internal organs, so the 'fat' will look like abdominal swelling, or the fluid could be more evenly distributed over most of the fish's body. A species with scales will take on a 'pine cone' look. Yoyo Loaches do not have scales to stick out in this manner.

[prince]

He's fat around his middle- it's evenly distributed on both sides, rather than all around. I don't know whether the fish is male or female.
Is it something I should ask a vet about?

I've recently bought a new yoyo loach (for unrelated reasons). I've been led to understand that they like to eat snails, and the tank has had a recent snail infestation- could that have something to do with it? If it is related to overeating for any reason, hopefully the new yoyo can take some of the food off his plate!

Thank you for responding :)

[Diana]

IME Yoyos are very good snail eaters, and are willing to burrow through the substrate.

It may well be that the single Yoyo was overeating on the snails, so a little competition may be just the right thing.