Is my Rainbowfish sick?

[Rainbowfish]

I believe my bosemani rainbowfish is ill, they have a curved spine, I originally suspected . Overall they seem perfectly healthy otherwise (eating normally, schooling with the others). I noticed some of my kuhli loaches losing weight and my hillstream loaches a bit pale so I’m worried it may be a parasite. It’s a 38 gallon tank with 2 bosemani rainbowfish, 8 kuhli loaches, 6 young dwarf neon rainbowfish and 6 hillstream loaches. My first thread sorry for being all over the place but I’m a bit freaked out. 

[eddie462]

Can you repost the picture please? The full size photo isn't appearing in your post. The small thumbnail photo shows a black banded rainbowfish with a curved spine. A detailed photo will help me.

From that photo the fish looks to be a Turquoise Rainbowfish, Melanotaenia lacustris. The black band is a giveway that your fish isn't M. bosemani. Bosemani rainbowfish do not have a black band. It also looks a little blue to me. 

Do you know how old the fish is? Rainbowfish will have their spines curve like that as they become old. The other thing is that a 38g tank at 30" L is too small for the two mentioned species. Both can grow up to 6" long, and a 4 foot long aquarium is the recommended minimum size for them.

Edited June 28, 2022 by eddie462
Adding full size photo sentence

[Rainbowfish]

I will in a minute thank you for your help. My local fish store wasn’t the best, they’re closed now so I can’t get any meds unless they’re online. I’ve had them almost 2 years and one has grown (the non deformed one) and the one with the curved spine hasn’t grown since I got it. Old age is a definite possibility and the kuhli’s might be thin because the much larger ones are bullying them off the food. 

[Rainbowfish]

Here’s a picture of my Rainbowfish and I added one of my pale Hillstream loach, he seems to have gotten some color back in the last couple days but he’s still much paler than some of my other ones that are almost black. I couldn’t find my thin Kuhli loaches but they seemed to be pretty close to paper thin. 

[eddie462]

That is a juvenile rainbowfish, as he's looks small (about 2") to me and doesn't have color. He may be born with that deformity or he could have swam into something and bent his spine. The good thing is that since he's young, that aquarium is an appropriate size for about a year. Your rainbowfish has a full stomach while you said the kuhli loaches were losing weight. Rainbowfish are quick to food, so he could be eating most of the food. Add in food for the bottom feeders at night to get past the rainbowfish. I would treat the whole aquarium with an anti parasite drug like Fritz Paracleanse. I used it once for worms and it cured my fish. If all of the bottom feeders have weight issues, it is likely that they contracted internal parasites from wholesale.

[Rainbowfish]

About 5 or 6 of my kuhli’s are well fed and healthy looking and 2 are pretty much paper thin, they’ve always been the smallest but it seems they’re getting thinner and thinner, I’m beginning to think maybe you’re right because I’ve seen the rainbowfish pick at algae tabs that I give to the bottom feeders pretty aggressively. It’s also very possible my rainbow-fish hit something like you said because the one with the bent back has been chased by the larger one for his whole life in the tank.  I’ll get some paracleanse from Amazon and treat the tank asap just in case. Is there anywhere you’d recommend buying a larger tank? I’ve heard horror stories about bigger tanks from petsmart having leaks and extremely cheap stands. I have an empty 55 tall in my basement but that barely gives them any extra horizontal room and it would be a massive pain to trade the tanks as my 38 is in literally the only place it can fit in my room. If I’m gonna trade tanks I’d want to make sure it’s a forever home for them. How big would you recommend? I was considering a 75 for some goldfish but I might just get that for these guys if it’s big enough. If not I’ll probably need to donate them somewhere when they get too big for this tank. 

Edited June 28, 2022 by Rainbowfish

[Mmiller2001]

This could be TB or defect. Keep an eye on things and wash your hands after entering the tank.

Edited June 29, 2022 by Mmiller2001

[eddie462]

On 6/28/2022 at 7:21 PM, Rainbowfish said:

About 5 or 6 of my kuhli’s are well fed and healthy looking and 2 are pretty much paper thin, they’ve always been the smallest but it seems they’re getting thinner and thinner, I’m beginning to think maybe you’re right because I’ve seen the rainbowfish pick at algae tabs that I give to the bottom feeders pretty aggressively. It’s also very possible my rainbow-fish hit something like you said because the one with the bent back has been chased by the larger one for his whole life in the tank.  I’ll get some paracleanse from Amazon and treat the tank asap just in case. Is there anywhere you’d recommend buying a larger tank? I’ve heard horror stories about bigger tanks from petsmart having leaks and extremely cheap stands. I have an empty 55 tall in my basement but that barely gives them any extra horizontal room and it would be a massive pain to trade the tanks as my 38 is in literally the only place it can fit in my room. If I’m gonna trade tanks I’d want to make sure it’s a forever home for them. How big would you recommend? I was considering a 75 for some goldfish but I might just get that for these guys if it’s big enough. If not I’ll probably need to donate them somewhere when they get too big for this tank. 

That's great that you'll get the medicine. After you dose Paracleanse, feed them well for a week. If they still have weight issues, then dose Fritz Expel P. Paracleanse treats tapeworms and flukes, while Expel P treats other parasites. It is hard to tell which is inside your fish. 

The rainbowfish that has the bent spine is less dominant than the other rainbowfish from your post, so he will continue to be bullied. After you treat for the internal parasites, add in more rainbowfish. Quarantine the new rainbowfish so that you don't reintroduce the same parasites if your get the fish from the same store. All rainbowfish are schooling/shoaling fish, and the recommended minimum school size is 6. Having more fish will distract the dominant male so that the subdominant male can get some rest.

There are horror stories with all aquarium sizes. It seems like its common when you see a post about a disaster frequently, but remember that the rest of the aquariums are still intact. A lot of those stories of aquariums from PetSmart and PetCo are the cheap Tetra brand aquariums that were sold for dollar per gallon sale aquariums. I have only been in the hobby for two years, and I haven't used nor seen Tetra aquariums in sales. Now it seems to only be Aqueon brand aquariums. The 55g Aqueon tanks used during 50% off sales and dollar per gallon sales have thin glass compared to tanks that weren't in the sales. I don't recommend those 55g tanks.

The six aquariums I have/had have all been intact. They were all used aquariums from friends or purchased on Facebook Marketplace. I have always checked the silicone beads on the inside. Also, as long as the glass doesn't look really thin to the eye, you will be safe. If you want to be sure, you can look up standard aquarium sizes and what thickness of glass is used for rimmed and rimless aquariums. 

Goldfish need about 25g per fish, so you could really only house three comfortably in a 75g. It would be best to put them into a very large aquarium or a pond. The 75g would be ideal for all of the fish in your 38g permanently. They can also go into a 4 ft 55g or the 4 ft 33g long aquarium. The 33g long is a 55g but shorter.