Molly acting weird. Maybe bottom sitting?

[mythonis]

Hi, having an issue with one of my marble mollies. He was fine yesterday and then today he seems to be having trouble swimming and spends all of his time sitting on the tank decorations (not sure if that counts as bottom sitting because he's not going to the bottom of the tank to sit on the sand, he's sitting on the rocks or the plants at about the mid-level of the tank). He still seems interested in food but swimming is obviously hard for him (he wiggles his head way more than he needs to, so it looks like he's swimming in a really exaggerated way) and if there's not food to be had, he doesn't move around much, just stays sitting on the rocks.

No ich, no velvet, no mites, no excess slime, his eyes don't look cloudy, his fins aren't clamped, he's not pineconing, and he doesn't seem bloated.
I have no idea what's wrong or IF anything is wrong. None of my other fish are acting weird right now, just the one molly.

29 gallon, partially planted, sand substrate on top of gravel, Penguin Bio Wheel 200 HOB filter. Cycled for 6 weeks, fishless. Fish added ~3 weeks ago.
3 black mollies, 1 angelfish, 2 marble mollies (and 1 teeny fry that has managed to avoid being eaten by the angelfish), 1 bristlenose pleco (currently ~2 inches long).
Temp 79F, pH 8, GH 180ppm, KH 120ppm, NO2 0ppm, NO3 30ppm.
Last water change was 20% done 2 days ago.

I know my nitrates are a bit high, I'm in the process of trying to get them down with PWC. And I don't have an ammonia test kit right now but the last time I checked (a couple weeks ago, just before I got my fish), it was at zero. It's entirely possible it's changed but I don't have a way to test it until I get paid again next week.

 

[ImACoolguy]

Can't really say what's wrong with the molly.. I've had lazy fish before what were perfectly fine but enjoyed laying on plants.

An API Fresgwater Master Test Kit will be the best "bang for your buck" after a year and multiple tanks I'm still using the same kit.

I'd keep doing PWC till you can check the ammonia. If it's not ammonia, well you gave them some nice fresh water anyway


Caleb

 

[mythonis]

Yeah, that's the plan. He's doing better today, swimming around like normal. It's really weird. My angelfish did the same thing a while ago, was acting lethargic and staying near the surface and red around the gills, and the next day he was fine and acting completely normal.
If I didn't know better, I'd think my fish were trolling me, hehe.

Thanks for the kit recommendation, I'll give it a look!

 

[ImACoolguy]

Yeah, that's the plan. He's doing better today, swimming around like normal. It's really weird. My angelfish did the same thing a while ago, was acting lethargic and staying near the surface and red around the gills, and the next day he was fine and acting completely normal.

If I didn't know better, I'd think my fish were trolling me, hehe.



Thanks for the kit recommendation, I'll give it a look!

Redness at the gills and hanging at the surface 95% of the time means ammonia burns.


Caleb

 

[mythonis]

Redness at the gills and hanging at the surface 95% of the time means ammonia burns.


Caleb

I would think that wouldn't just go away, though, not as long as the ammonia levels were too high and my angelfish looks fine now, this is what's mystifying. My angelfish was acting weird and looked irritated and then 24 hours later was fine, swimming normally and no redness, and he's had no problems since. He was also the only fish in the tank that looked irritated or was having any trouble. It was right after a water change so I figured that's what had caused it. I've had fish before that were just irritated by water changes.

So, basically, I did a water change and the next day my angelfish started acting sick, 24 hours later he's fine. The day after my angelfish seems to get better, one of my mollies starts sitting on the decorations and having a hard time swimming, 24 hours later (today) he's fine. And this entire time none of my other fish have any redness or other obvious problems or are acting other than normal.
I have no idea what's going on. As far as I'm aware, tank-wide problems like ammonia and nitrate issues effect all fish in the tank. I have no clue what could make fish take turns looking ill (with different symptoms) while all the other fish seem fine.