Does this look like aggression?

[Spoolin]

Hi everyone-

My 40g breeder tank currently has 10 Rummy Nose Tetras, 12 Cardinal Tetras, and 1 Hillstream loach. 
 

I’ve noticed that the Loach would dive upwards and downwards at the tetras during the evening after 7pm before lights shutoff at 9pm. I’ve had this Loach for about 7-9 months and it just recently started doing this. Is this aggression or playing? Lol 

 

 

[TheSwissAquarist]

Looks like he’s defending a sort of territory to me.

I’ve had the same problem in the past, and solved by adding another loach because they’ll either breed or fight against each other instead of other fish.

[nabokovfan87]

On 10/23/2022 at 8:08 PM, Spoolin said:

I’ve noticed that the Loach would dive upwards and downwards at the tetras during the evening after 7pm before lights shutoff at 9pm. I’ve had this Loach for about 7-9 months and it just recently started doing this. Is this aggression or playing?

It isn't aggressive, it's fear to me.  Both the tetras and the schooling/shoaling fish want to have some place to go through, to go towards to swim around.  Adding a piece of wood, a rock pile, it would immensely change the chemistry in the tank for all of the fish. The loach thought it was going to be attacked or it thought that it doesn't have a place to go towards and so it tried to go somewhere, but it doesn't really have a cave.

Most loaches like that would end up in a shade spot, usually the back wall of the tank. The way the fish are acting makes me think the majority of them are stressed.

[TheSwissAquarist]

On 10/24/2022 at 8:30 AM, nabokovfan87 said:

Adding a piece of wood, a rock pile, it would immensely change the chemistry in the tank for all of the fish. The loach thought it was going to be attacked or it thought that it doesn't have a place to go towards and so it tried to go somewhere, but it doesn't really have a cave.

True, but it also seemed to be chasing a couple of tetras. Attacking them before they attack it?

Edited October 24, 2022 by TheSwissAquarist
Spolling

[nabokovfan87]

On 10/23/2022 at 11:31 PM, TheSwissAquarist said:

True, but it also seemed to be chasing a couple of tetras. Attacking them before they attack it?

I view it as the loach is trying to find a spot to rest, but can't. I would expect the Sponge filter or the back of the tank. It's in the center of the tank under the most lit part of the tank.  It's an odd place for that loach to protect. It's open, so to speak, because those fish want a flat surface to graze on. Mine would hang on and in a pleco cave. Add a ceramic pot or two and you're talking about a very different tank behavior.

Edited October 24, 2022 by nabokovfan87
edit video

[Odd Duck]

I agree with @nabokovfan87, that kiddo needs some hiding places.  As an example, fearful dogs are by far the most likely to bite.  They are on edge and always ready to defend themselves.  That poor loach is terrified.  I can almost guarantee that some good places will solve this problem completely.

[RockMongler]

Yeah, I would 100% get some rounded cobbles or a good piece of wood or something to act as a line of sight blocker/a place to hide.  I have a few hillstream loaches in my 20W and they spend a lot of their time just chilling in areas of high flow, or in places that they feel" hidden".  I almost never see my loaches swimming around in open water like that.  They almost entirely stay low, and they "hop" from surface to surface in a manner that reminds me of watching a gecko navigate their environment.  They only swim higher like that if they are chasing each other around for a moment or two, before they settle back down into their "chill" spots.  Attached is a semi-recent photo of my tank.  There are two hillstream loaches that live in here, and they often hang around in the pile of cobbles below the powerhead to the right side of the tank, the single big cobble more to the left, or near the airstone.

[Chick-In-Of-TheSea]

I'd think something like this would help him find comfort.  (Don't get the floating one though - this one here is ceramic and will sit on the substrate).

 

[nabokovfan87]

They also love big pieces of Mopani!  If you don't see a good one in the fish section, double check the lizard side of the shop and they might have flat pieces for perching.  Same wood, same tags, they literally just sort them differently based on placement.