Semilarvatus Pair Behavior

[Steve and his Animals]

I recently (a little under 3 weeks ago now) acquired a pair of Chaetodon semilarvatus. The smaller of the two had a poor appetite and died the next day, so I got a replacement. The two have been sitting in quarantine for over a week together, and today I noticed the larger (original) one was being very territorial during feeding time. Checking on them a few hours later, I see no outward aggression but the smaller one seems nervous around the larger one without any provocation.

My question is, will this pass at some point? I know butterflies are gonochoristic so I very well could have gotten two of the same gender, I just didn't know if anyone else had experiences like this that ended with a happy couple anyway.

Quarantine is a 15 gallon plastic tote, about 24-28in long and 16in wide. I know it's small, but it's a quarantine.

Should I try getting a third and seeing what happens? Replace one? Any advice/personal experiences would be appreciated.

 

[Montiman]

While I don't have any large Chaetodon species now I worked for years at an LFS that catered to Fish Only Aquariums. We sold many butterfly pairs and kept a few at the shop.

My experience is that there may always be some aggression but it can likely be managed. If both fish are eating well and the less dominate fish is not showing physical trauma I would not worry. Once the fish are added to a large display with more room and more distractions the aggression will likely subside and become manageable. One thing many people miss with large fish systems is that some aggression is normal and needs to be managed not eliminated.

 

[Steve and his Animals]

While I don't have any large Chaetodon species now I worked for years at an LFS that catered to Fish Only Aquariums. We sold many butterfly pairs and kept a few at the shop.

My experience is that there may always be some aggression but it can likely be managed. If both fish are eating well and the less dominate fish is not showing physical trauma I would not worry. Once the fish are added to a large display with more room and more distractions the aggression will likely subside and become manageable. One thing many people miss with large fish systems is that some aggression is normal and needs to be managed not eliminated.

I'm not as worried about the aggression, butterflies in my experience rarely hurt each other, I'm more concerned with having a truly mated pair. I used to see pairs of wild butterflies when I lived in Hawaii, and I always loved how closely they swam together and everything. I want it to be the centerpiece to my tank, not really looking for just two of the same butterfly wandering aimlessly lol. I know it sounds picky and choosy but it's just part of why I like the fish group so much.

 

[Montiman]

True pairs are hard. You are really just guessing unless you can witness the paired behavior. This is particularly true of small fish. Often the pairs won’t act like the pairs we see when diving until they are very large.

 

[Steve and his Animals]

True pairs are hard. You are really just guessing unless you can witness the paired behavior. This is particularly true of small fish. Often the pairs won’t act like the pairs we see when diving until they are very large.

Good point, they are both only in the 3-4 inch stage right now. Hopefully things change when they move into the final display in a couple weeks.

 

[Big E]

You may just luck out and have a pair as your chances are basically 33%.

When I had semis I bought 4 all at the same time. I was lucky in that they paired off into two pairs. I had to keep the pairs separated as I only had a 75g and one pair was always dominant. It was never physical harm as much as bullying and forcing fish into a corner and constant chasing which is just as bad due to stress and not being able to feed good.

When I went to a 180g I was able to put all 4 together. I later added two more but couldn't keep six. One of the new ones got bullied, so I ended up with 5 in my 180g.

What size tank are they going into? These guys grow very slow and won't get much bigger than 5-6". Mine were all in the 4" range when I got them.

I kept them for about 5-6 years before they started to die from various internal or bacterial diseases.

 

[Steve and his Animals]

You may just luck out and have a pair as your chances are basically 33%.

When I had semis I bought 4 all at the same time. I was lucky in that they paired off into two pairs. I had to keep the pairs separated as I only had a 75g and one pair was always dominant. It was never physical harm as much as bullying and forcing fish into a corner and constant chasing which is just as bad due to stress and not being able to feed good.

When I went to a 180g I was able to put all 4 together. I later added two more but couldn't keep six. One of the new ones got bullied, so I ended up with 5 in my 180g.

What size tank are they going into? These guys grow very slow and won't get much bigger than 5-6". Mine were all in the 4" range when I got them.

I kept them for about 5-6 years before they started to die from various internal or bacterial diseases.

They're going into an Oceanic 90 gallon, which is 5ft x 18" x 18" instead of the standard taller 75.

The chasing isn't constant which is odd, it seems to only be during feedings, unless I haven't been sitting in front of the quarantine long enough at one time to notice. That's why I don't know if this is just a space thing but it doesn't make sense to me why the larger one would chase the smaller out of feedings if they were going to pair off. Maybe they haven't made that decision yet. Who knows? I'm not very optimistic since I believe I've seen pearlscale pairs act much nicer with each other starting at a smaller size, but like I said I don't know if it's just a function of the QT size that is stopping them.

 

[Big E]

Initially that doesn't sound good. The mild soft aggression is when one will nip near the anal fin of the other but not do damage or chase.

I'm not sure how much growth you'll get but try to keep the rock work open and don't overpopulate the tank.

Try to keep the water pristine.........I would run carbon and a UV sterilizer full time.

They eat almost anything so try to keep them full bodied and feed a lot.

 

[Steve and his Animals]

Initially that doesn't sound good. The mild soft aggression is when one will nip near the anal fin of the other but not do damage or chase.

I'm not sure how much growth you'll get but try to keep the rock work open and don't overpopulate the tank.

Try to keep the water pristine.........I would run carbon and a UV sterilizer full time.

They eat almost anything so try to keep them full bodied and feed a lot.

What sounds bad? The tank size or the aggression? It's not like the smaller one isn't getting any food, the big guy is just pushing him out of bits here and there, but they both have decent bellies, no pinching above the head or any other signs of emaciation.

I'm specifically running coppersafe and general cure in the water/food so they have a healthy and clean start in the display. The rockwork is very open, most of it is tall and centered with caves, with a couple tables on either side, but a lot of open swimming space. The only tankmates in there right now are golden angel (C. aurantia), a Coris pictoides, a staghorn damsel, and an indigo dottyback.

The other fish in the QT are a yellow banded possum wrasse (W. nigropinnata), a scribbled boxfish female (O. solorensis), and a swissguard basslet (L. rubre). The only other fish I would consider putting in the tank would be a pair of sand sifting gobies/pearly jawfish or a single blue spot jawfish. Haven't decided yet, but that's really as much stocking as I'm comfortable with.

 

[Big E]

The chasing off during feeding could lead to more aggression later..............just going off your observations. I never had aggression during feedings with any of mine.

 

[Steve and his Animals]

The chasing off during feeding could lead to more aggression later..............just going off your observations. I never had aggression during feedings with any of mine.

Yeah I figured as much, thanks for the advice.

 

[MrsBugmaster]

I've had the best luck forming pairs by buying 5 small and medium (different sizes) and put in qt all together. It took a few months but eventually I got a pair. I did use a 55 gallon tank too so they had more room. I did the Indian Vegabond butterflies so they are much cheaper than the semilarvatus, so I understand this may be cost prohibited. Then I would sell off the others.

 

[Steve and his Animals]

Just as an update, I was very hesitant to move them to the display for months because of I did truly want a pair out of them, but I felt bad leaving them in QT even though I upgraded to a 40-gallon tote awhile ago. In the meantime, I added a third smaller semilarvatus, and he was even more shy and hesitant to approach the initial two than I expected. Long story short, the little guy never put on any weight no matter what he ate, even after extensive deworming, and eventually passed. I decided to move the big guys into the display after that for various reasons, and, surprisingly, they spend quite a bit of time together. Maybe I lucked out and they just needed some time/new territory to really get along like a pair, or they're just playing nice. Either way they seem happy so I'm happy enough. Maybe I'll try adding another pair later on to see who they like and rehoming the two that aren't part of the happy couple.

Also, as a side note, I always like experimenting with corals and butterflies, since I'm okay removing corals since I prefer fish in this hobby. Surprisingly, the first coral they nibbled which I never expected them to was a colony of Palyxanthoa and it seems they are also nibbling one of my two Euphyllias, but not the wall hammer. I specifically mention the hammer because I've had previous butterflies of different species with the same reaction: nibbling other LPS but not touching the hammer. Maybe it has something to do with a stronger sting? Color? Who knows, just thought that was interesting.