Help - loaches are dying

I have a 25 litre tank for a beta and 4 small algae eating shrimp. We recently bought 4 ota loaches from Pets at Home on offer - however after 6 days 2 suddenly died. I tested the water and it was fine and also had it tested in the shop. They replaced the 2 fish with 2 more otas but tonight 2 more suddenly died! The other 2 appear healthy as does the beta so I can't understand why. It's an established tank and we're only feeding frozen live food (daphnia, cyclops, and blood worms) so I don't think it can be to do with waste food gases as we only feed enough that the beta eats. The lights are on all day and evening to ensure algae growth, although the loaches seem really efficient at cleaning the glass as I haven't had to scrape it once since purchasing them and previously I was cleaning it every week. Is it possible they are starving as there isn't enough algae or are they stressed by the shrimp? I'm really puzzled and don't want to lose the 2 remaining loaches.

What species are the loaches? Search "ota" turned up nothing.

First thing that comes to mind is that this 6 gallon tank is very much over stocked.

I don't think it's overstocked as the shrimp are tiny, as are the loaches and there's just one betta.

The fish are in fact catfish (not loaches, my mistake) and are otocinclus. I've just ordered some algae pellets to feed them in case there isn't enough algae in the aquarium for them (although I can see it growing on the rock and plant). It's just odd that in 2 instances, 2 fish died within an hour of each other and were seemingly very healthy prior to that and the water parameters are testing as perfect.

Otocinclus are algae eaters with a large requirement for oxygen. A tank they'd flourish in would kill a Betta, as they need moving water. Bettas, with the mutant fins, would be blown around and die of exhaustion. Your store is not giving good tankmate advice.

I have never, ever, anywhere bought delicate fish on sale without losing at least half of them in the first week. There's that too. They've been shipped, kept in a stressful shop tank...

Otos are very sensitive fish. Many are on the point of death when they arrive at a shop. Never buy otos unless they have been in the shop at least two weeks so the weak ones have already died. Always look for otos with rounded tummies as this shows they are eating well. But not huge tummies as those are sick.

Many otos will only eat one species of algae. They won't eat algae pellets or anything but one type of algae, and that may not be the one growing in a tank. yes some do learn to eat several food, but many do not and they starve to death.

Otos also need a larger tank than this; a small tank cannot grow enough algae to feed a shoal. Not to mention the fast water flow as Gary said.




Did you get the fish from Pets@Home, Maidenhead Aquatics or an independent shop?

I concur with previous members on the tank size and the otocinclus problems. You can manage the betta in this small a tank, and shrimp (unless the betta decides to eat them), but no other fish. As for otocinclus, they are always a risk as others have indicated, I would not get more.

Thanks for all the advice. @Essjay yes, from PetsAtHome. I'm really disappointed by this because I genuinely love fish and had good intentions and didn't want to behave like a novice but it's been many years since I last kept fish and thought that these bottom feeders would be fine in the tank. For context, I use to keep fish for years and had a 300 litre cichlid tank (Malawi cichlids) years ago that I then turned into an oscar tank once I relocated and had to give away the cichlids. This little tank was bought for my son during the lockdowns in 2020 as an introduction to fish keeping and for something to entertain him whilst we were all locked up at home. We had a few guppie for 2 years but when they died I decided to just keep 1 betta in the tank with some shrimp we've also had for about 2 years and then saw these oto's and decided to add them. The shop has offered me 2 free replacements but I turned them down and I said I don't want to introduce anymore fish to the aquarium. I hope the 2 remaining ones will be fine but from here on out it will just be a betta tank.

honestly...oto's are known as algae eaters that barely eat any algae xD
they're probably dying of starvation as they're starving coming from fish farms
go on amazon and search for spirulina algae wafers
I use this one:
and as my otos and snails and shrimp are in the same tank... I have 2 otos in my main and 1 single regular oto and 2 zebra otos in the shrimp tank
the shrimp tank I only feed 1 of these pellets every 3-4 days and that's probably around 50 shrimp 3 otos and a bunch of ramshorn snails that I use to dump in my main tank for my pea puffers

Pets at Home has a poor reputation, though some branches are better than others.

Never take advice from any fish shop as staff are trained in how to sell not care of their stock. That includes chains and independent shops.

kiko said:

honestly...oto's are known as algae eaters that barely eat any algae xD
they're probably dying of starvation as they're starving coming from fish farms
go on amazon and search for spirulina algae wafers
I use this one: View attachment 307198
and as my otos and snails and shrimp are in the same tank... I have 2 otos in my main and 1 single regular oto and 2 zebra otos in the shrimp tank
the shrimp tank I only feed 1 of these pellets every 3-4 days and that's probably around 50 shrimp 3 otos and a bunch of ramshorn snails that I use to dump in my main tank for my pea puffers

Click to expand...

Thanks for the feedback, I actually ordered some algae wafers (Heron's Pet World brand) from Amazon yesterday and they're arriving today.

Essjay said:

Pets at Home has a poor reputation, though some branches are better than others.

Never take advice from any fish shop as staff are trained in how to sell not care of their stock. That includes chains and independent shops.

Click to expand...

I generally don't unless it's an independent shop. It's just I've been out of the fishkeeping circle for over 10 years and didn't do my research. Ultimately one day I'd love to have another 300 - 500 litre aquarium for cichlids but that won't be until I move to a larger property.

kiko said:

honestly...oto's are known as algae eaters that barely eat any algae xD

Click to expand...

Not true.

Otocinclus are voracious algae eaters; many times, there's not enough algae in a tank that isn't well established for them to have enough to eat

well I can tell you hillstream loaches clean up algae really nice and otos barely cause a dent
doesn't change the fact his otos are dying
my otos don't die and at 50bucks a fish I wouldn't rely on algae alone even if they did
a common oto you can get for 4 bucks...not zebra otos