Blenny attacking conch

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Lyss

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I have a tailspot blenny that has been in my tank almost a year, since the tank was cycled and ready for fish. Within the next month he was joined by two clowns, and the first group of CUC. Then about a month later a cleaner shrimp.

Blenny is friendly w/the shrimp — lets himself be cleaned sometimes, and also w/the clowns. He pushes hermits and snails off his home rock if they get too close to his barnacle house, but up until now I’ve never seen him full on attack anything.

Three times now since I added a strawberry conch a couple weeks ago I’ve seen him attack it. These attacks happen at night, and when the conch is spotted on a rock, but not anywhere near the blenny’s home rock. So far the conch has only been a bit shaken but unharmed, but I’m starting to get worried that he might hurt it.

Are tailspots known to become aggressive? I was under the impression that they were very peaceful in tanks except with their own kind. I’m not sure if there’s anything I can do in this situation. He appears to get pretty agitated when he spots the conch on any rock at night, attacks, and then swims in and out of his barnacles eyeing it like he’s prepared to strike again.

This all also has me worried about ever adding another fish. I’d hoped to add a pink streaked wrasse at some point, but that fish will be in the rockwork. Kinda afraid now that the blenny thinks the rocks are all his territory. He doesn’t attack the clowns when they come close but they’ve been in the tank together as babies this whole time.
 
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Lyss

Lyss

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is the blenny going for the shell or the conch?
The face! He’s def going for the animal and not the shell. It’s looks like a clear aggressive strike to make it leave the rocks.

Edit: he clearly isn’t hurting it so far. But he goes right for the front of the shell where the animal is.
 

shakacuz

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it could just be a territorial thing. my midas blenny is similar in behavior about the opening to his little cave/porch. will lunge/nip at anything that passes close by to his cave opening
 
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it could just be a territorial thing. my midas blenny is similar in behavior about the opening to his little cave/porch. will lunge/nip at anything that passes close by to his cave opening
Yeah that makes sense and he does push hermits and snails off the rock where his home is; but this w/the conch is basically any rock, not even close to his home. He appears to think all of the rocks are his territory when it comes to the conch and only has it out for this particular animal in this way.
 
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Lyss

Lyss

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I think I need to see a picture of your tank.
Hers the blenny in question, and then here’s the most recent photo I have — there are more corals and some macroalgae on the rocks now. It’s hard to get a good full tank shot b/c where it’s placed there’s a lot of glare. It’s a max nano.
 

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blaxsun

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I think I see why your blenny is ticked - you need a bigger tank! The barnacle "hotel" that my midas blenny occupies is about 1/3 the size of your rock face (blennies like their barnacles and rocks!)

9BBA4A45-7ACB-4C6E-812C-9DB530070531.gif
 
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Lyss

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I think I see why your blenny is ticked - you need a bigger tank! The barnacle "hotel" that my midas blenny occupies is about 1/3 the size of your rock face (blennies like their barnacles and rocks!)

9BBA4A45-7ACB-4C6E-812C-9DB530070531.gif
Hmm, well that’s 18 lbs of rock lol so I’m sure the 4-inch barnacles are not 1/3 of it. He also lets everyone else go on the rocks just fine — the shrimp is even right outside his home in the pic, though like I said he does push snails and hermits off when they go where the shrimp is, but not always. The conch’s existence in particular agitates him in a way I’ve not seen before.
 
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Lyss

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Blennies are actually bold little ***** and can be territorial. This isn’t unusual behavior even for a tailspot.
Lol. Well in a weird way I’m glad to see some boldness out of him b/c he was always the more timid of the group. Now that I think about it, in the past month or so he’s only just begun using more of the rock work vs staying in his area — going in the caves and swimming through/all around it.
 

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Hmm, well that’s 18 lbs of rock lol so I’m sure the 4-inch barnacles are not 1/3 of it. He also lets everyone else go on the rocks just fine — the shrimp is even right outside his home in the pic, though like I said he does push snails and hermits off when they go where the shrimp is, but not always. The conch’s existence in particular agitates him in a way I’ve not seen before.
My barnacle hotel is about 10” x 8” x 6” they’re rather large barnacles and about 12 of them).
 
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Lyss

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My barnacle hotel is about 10” x 8” x 6” they’re rather large barnacles and about 12 of them).
Oh, I see what you're saying. But no, a bigger tank is not a consideration for me. Bigger bigger bigger is not gonna be a solution for me in my current space. These fish are said to need a 10g + tank, so 20g isn't grossly too small for him. I may just not be able to have 4 fish now.

Edit: He's fine w/the conch during the day, it's at night. But then, at night is when it dares to venture onto a bit of rock now and then, and that seems to draw the Blenny's ire.
 
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I'd love to see a video of it if you can get one. My tailspot blenny "grazes" on anything, but specifically targets hermits and astrea snails and sometimes knocks them off the rocks. He'll even "graze" on my arm hair if I'm mounting a coral in the tank (scared the life out of me the first time he did it). I know they can be territorial, but it's bizarre that he's targeting your conch this way.
 
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Lyss

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I'd love to see a video of it if you can get one. My tailspot blenny "grazes" on anything, but specifically targets hermits and astrea snails and sometimes knocks them off the rocks. He'll even "graze" on my arm hair if I'm mounting a coral in the tank (scared the life out of me the first time he did it). I know they can be territorial, but it's bizarre that he's targeting your conch this way.
I'll try to get one -- the problem is when it happens, it's at night, and I'd prob need to set up a camera on a tripod to see if I can get it b/c it happens quickly. It was odd to me, too, since all I've known him to do is nip at hermits and snails to turn them away or push them off his house -- edit: this is different from the grazing, which he will also do, this is specific to when one goes on his barnacles and he doesn't like that, so he pops out and nips at it to make it go . W/the conch he zips over to wherever it is and really aggressive bites, then zips back to his house.

The poor thing just tucks into its shell for a while, I take it of the rocks and place it back on the sand, and then it goes back about its business. But I do see the blenny eyeing on the sand like he's thinking of a 2nd strike -- haven't seen him do a 2nd strike yet tho.
 
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TnFishwater98

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Hmm, well that’s 18 lbs of rock lol so I’m sure the 4-inch barnacles are not 1/3 of it. He also lets everyone else go on the rocks just fine — the shrimp is even right outside his home in the pic, though like I said he does push snails and hermits off when they go where the shrimp is, but not always. The conch’s existence in particular agitates him in a way I’ve not seen before.
I just added a tailspot 20 min ago. I’ll watch his behavior. But as far as LR, you probably should have around 40lbs if that’s a 20 gallon , IMO.
 
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I just added a tailspot 20 min ago. I’ll watch his behavior. But as far as LR, you probably should have around 40lbs if that’s a 20 gallon , IMO.
The display is 16 gallons, the rest is the back sump. I have about 18-20 lbs of rock in there and the space is full.

A portion of what couldn't fit in the display is in the sump. I was always told 1 lb per gallon, not 2...
 
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