my teacher's fish tank is being conquered by territorial hillstream loaches

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Let's look at what went wrong here.
A fish most posters believed could not be aggressive was aggressive. Most online research will say that they are community fish, clearly. Most experienced fishkeepers here said that earlier in the thread.
The teacher did not have the Latin name, and used the trade name. I'm sorry but a minority of people who post here know the real names of their fish, and go with names of local stores or importers. Confusion with trade names is a feature here, and I have been criticized for using internationally recognized names because they aren't English.

If I hadn't had a psycho Sewellia, I would have accepted they're peaceful. If I hadn't seen obscure video on adaptations to fast water, it wouldn't have crossed my mind that current could control aggression. It never occurred to me when I had them., only after when I saw current used to control aggression in Geophagus argyrostictus, a rowdy member of a generally calm Genus.

So, if the teacher looked up the fish, they probably would have done what was done. The Sewellia were observed attacking, a legit observation.

If it had been a common pleco, how many of you would honestly observed they are often found close to outflows?

I don't think the hillstream loaches actually were seen aggressing in this case? He said they thought that because they had some losses after getting them, but that they'd bought other fish too. As far we know, there could be a small snakehead in there, going to town. But, it's a long thread, and I may have missed something.

You're right that even if he'd done in depth research, most sources would say peaceful, not a problem in a community, so he's not at fault even if they are the problem in the tank. But I thought we were now talking in general terms about teachers being busy, so relying on faulty fish store advice is okay.

But, I'm breaking my own rules there by being harsh I suppose, since if a beginner comes here wanting help because they relied on bad fish store advice, I always say that it's understandable, that it makes sense to trust that the fish store people should know what they're saying, of course most people will listen to them. So... I dunno. I don't even believe in my own point anymore... I just wish more people would care about looking into the animals they keep, before buying them. I've also seen some rescued snakes that were abandoned classroom pets and had been horribly, permanently deformed as a result of completely inappropriate conditions, and the fish that some science teachers have used as part of some cruel 'experiments', where they stick a feeder goldfish or betta in a cut off plastic bottle and stick a plant in the top, type of thing. Some really upsetting classroom pet stories out there.
 
Let's look at what went wrong here.
A fish most posters believed could not be aggressive was aggressive. Most online research will say that they are community fish, clearly. Most experienced fishkeepers here said that earlier in the thread.
The teacher did not have the Latin name, and used the trade name. I'm sorry but a minority of people who post here know the real names of their fish, and go with names of local stores or importers. Confusion with trade names is a feature here, and I have been criticized for using internationally recognized names because they aren't English.

If I hadn't had a psycho Sewellia, I would have accepted they're peaceful. If I hadn't seen obscure video on adaptations to fast water, it wouldn't have crossed my mind that current could control aggression. It never occurred to me when I had them., only after when I saw current used to control aggression in Geophagus argyrostictus, a rowdy member of a generally calm Genus.

So, if the teacher looked up the fish, they probably would have done what was done. The Sewellia were observed attacking, a legit observation.

If it had been a common pleco, how many of you would honestly observed they are often found close to outflows?
And a lot of people will see natural behaviour, courtship, mating etc... as agression. How many threads have been on here about "agressive" fish which appeared to show completely normal behaviour.
Even Corys of certain species often are said to be agressive (when mating) though they are mellow and not even capable to be agressive.

Behaviour of fish is often misunderstood and when agression is an issue often caused by humans.

The fact that you seem to have had a psycho Sewellia doesn't mean we have to do with an agressive species at all. I think they aren't a communityfish btw cause of their needs.

If the Sewellia have bred in the tank, it could be so crowded they "fight" for their place. I simply don't believe they could have killed a Cory (they even don't have the "weapons" to do so.
 
And a lot of people will see natural behaviour, courtship, mating etc... as agression. How many threads have been on here about "agressive" fish which appeared to show completely normal behaviour.
Even Corys of certain species often are said to be agressive (when mating) though they are mellow and not even capable to be agressive.

Behaviour of fish is often misunderstood and when agression is an issue often caused by humans.

The fact that you seem to have had a psycho Sewellia doesn't mean we have to do with an agressive species at all. I think they aren't a communityfish btw cause of their needs.

If the Sewellia have bred in the tank, it could be so crowded they "fight" for their place. I simply don't believe they could have killed a Cory (they even don't have the "weapons" to do so.
When I thought my gudgeons were being aggressive, I later found out they were mating. Even though at first they were aggressive with how they did it, now they are more loving lol
 
Just throwing fuel on the fire here. What if the teacher was told to set up an aquarium by their supervisor or the owner of the school?
eg: Teacher Bloggs, we would like you to have an aquarium in your class.
Teacher responds with "I don't know anything about fish"
Teacher's Boss says "we want an aquarium in the classroom"

Anyway, I think this thread has run its course with teacher bashing. Move along everybody, nothing more to see here.
 
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Update: me and my teacher are brainstorming ideas to maybe increase the current in the tank or find a way to make the loaches happy. as for research I do belive that he did make a mistake when he only checked the website for information but as far as I can tell the only problems the loaches face are the water speed issues. I am making a tank at home and I might end up adopting them, But I think think it would be better for them to be in a big tank as they are. an idea me and my teacher had was to point the filtre closer to the wall so that there would be an area were the current is fast but the rest of the tank isn't disturbed. However it sounds to easy of a solution. What do you think?
 
Just throwing fuel on the fire here. What is the teacher was told to set up an aquarium by their supervisor or the owner of the school?
eg: Teacher Bloggs, we would like you to have an aquarium in your class.
Teacher responds with "I don't know anything about fish"
Teacher's Boss says "we want an aquarium in the classroom"

Anyway, I think this thread has run its course with teacher bashing. Move along everybody, nothing more to see here.
my teacher actually got it from the previous owner of the class. probably hard to move 2 entire 40 gallon tanks around especially if they moved countries. My teacher probably didn't have a choice.
 
And a lot of people will see natural behaviour, courtship, mating etc... as agression. How many threads have been on here about "agressive" fish which appeared to show completely normal behaviour.
Even Corys of certain species often are said to be agressive (when mating) though they are mellow and not even capable to be agressive.

Behaviour of fish is often misunderstood and when agression is an issue often caused by humans.

The fact that you seem to have had a psycho Sewellia doesn't mean we have to do with an agressive species at all. I think they aren't a communityfish btw cause of their needs.

If the Sewellia have bred in the tank, it could be so crowded they "fight" for their place. I simply don't believe they could have killed a Cory (they even don't have the "weapons" to do so.
I think you are right, maybe my teacher could set up a camera to see if it is another fish. we haven't seen any sick fish so it might just be something else in the tank.
 
WE FOUND THE PROBLEM (I think): The hillstream loaches are getting confused and attacking sterbai cories, (They have the same pattern on their skins and are also bottom feeders.) the loaches are trying to top them because they think the cories are opposing males. my teacher has actually seen them topping them. it makes sense that the cories would die because they dont have the evolutinary information that tells them how to escape.
 
WE FOUND THE PROBLEM (I think): The hillstream loaches are getting confused and attacking sterbai cories, (They have the same pattern on their skins and are also bottom feeders.) the loaches are trying to top them because they think the cories are opposing males. my teacher has actually seen them topping them. it makes sense that the cories would die because they dont have the evolutinary information that tells them how to escape.
It doesn't make sense at all cause Sterbai will use a poison to escape when attacked / stressed. The hillstreamloaches would be the first to die.

What are the fish fed? Can you show some pics of the tank? How.many fish are in at this moment?
 
It doesn't make sense at all cause Sterbai will use a poison to escape when attacked / stressed. The hillstreamloaches would be the first to die.

What are the fish fed? Can you show some pics of the tank? How.many fish are in at this moment?
okay, I didn't know that.

I will see to finding that info (its not my tank so it might take a while) but I do know that the fish are fed slow sinking pellets, i know this because I personally feed them voluntarily. If its a company name you are looking for then I don't know right now I might be able to get back later.
 
Loaches and catfish should generally be kept in separate tanks. Too many bottom dwellers is never a good mix. :)

What other fish are in the tank?
You could angle the filter outlet down one side to increase water movement there. You could also have a small power head/ internal power filter in the aquarium and put it on a timer. Have it come on for a few hours each day so the loaches can have some current to swim into, and the other fish can get some exercise, but they can also rest most of the day because the power head would only be on for a few hours each day. You could even have it on for 30 minute intervals 3 or 4 times a day.
 
Loaches and catfish should generally be kept in separate tanks. Too many bottom dwellers is never a good mix. :)

What other fish are in the tank?
You could angle the filter outlet down one side to increase water movement there. You could also have a small power head/ internal power filter in the aquarium and put it on a timer. Have it come on for a few hours each day so the loaches can have some current to swim into, and the other fish can get some exercise, but they can also rest most of the day because the power head would only be on for a few hours each day. You could even have it on for 30 minute intervals 3 or 4 times a day.
my teacher thought of tilting the filtre outlet as well, but that idea sound pretty nice as well. Also the cories went exctinct in the tank after the final one died a while back. as far as i can tell there is only a few fish down there other than the loaches. they are catfish but seem to be doing fine (there might be some kuhli loaches down there too.) but they are all in a 40 gallon so i dont think space is an issue.
 
First, there has to be an admission on the part of the teacher and anyone else involved in maintaining this tank that the fish species combination is not suitable from the perspective of the requirements of each species as well as the tank size. Once that is understood, some of the fish must be rehomed to other tanks, a store, a hobbyist. The aim being to only have compatible species suited to the tank space, the water temperature, the water flow, the aquascaping.

Until the above occurs, one or more of the species in this tank are going to be at a serious disadvantage, and that means poor health, ongoing problems, and to be honest inhumane conditions.
 

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