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Rabbitfish/Foxface growth rate

ThRoewer

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A couple of months ago I bought 2 Foxfaces, a tiny of maybe an inch and a half and a slightly larger of maybe 2 inches total length. They grew already a bit while in quarantine in a 10 gallon tank, but after I added them to my 100 gallon tank they really grew a lot. The large one is now at least 4 inches while the smaller is at a minimum 3. If they continue growing like this they will be the largest fish (that title is currently shared by the Maldives Regal male and the Marine Betta male) in the tank by the end of the year. The large one is already close to matching my bicinctus female in size.

Will they adapt to the tank in their size or will they grow until they reach their maximum size (which would be about a foot in length)?
 

Jay Hemdal

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A couple of months ago I bought 2 Foxfaces, a tiny of maybe an inch and a half and a slightly larger of maybe 2 inches total length. They grew already a bit while in quarantine in a 10 gallon tank, but after I added them to my 100 gallon tank they really grew a lot. The large one is now at least 4 inches while the smaller is at a minimum 3. If they continue growing like this they will be the largest fish (that title is currently shared by the Maldives Regal male and the Marine Betta male) in the tank by the end of the year. The large one is already close to matching my bicinctus female in size.

Will they adapt to the tank in their size or will they grow until they reach their maximum size (which would be about a foot in length)?
You're no doubt aware of the (false) idea of "fish growing to fit the size of the tank". Juvenile fish seem to grow much more rapidly than larger fish, but that is actually not so true if you measure growth by mass and not length (as fish get larger, they tend to increase in mass more than grow in length).

I think you are overestimating the full adult size for a foxface. I've got a group in a 90,000 gallon tank that have been there for 5 1/2 years and they are about 5" long. Fishbase lists the normal adult size as 9". A survey that I did some years ago though indicated that captive fish only reach about 80% of the full adult size listed by Fishbase, so a tad more than 7" in this case.

That said - I think your 100 gallon is going to be pretty crowded when these fish all max out (do you have more than the 5 fish you listed?).

Jay
 
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ThRoewer

ThRoewer

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You're no doubt aware of the (false) idea of "fish growing to fit the size of the tank". Juvenile fish seem to grow much more rapidly than larger fish, but that is actually not so true if you measure growth by mass and not length (as fish get larger, they tend to increase in mass more than grow in length).

I think you are overestimating the full adult size for a foxface. I've got a group in a 90,000 gallon tank that have been there for 5 1/2 years and they are about 5" long. Fishbase lists the normal adult size as 9". A survey that I did some years ago though indicated that captive fish only reach about 80% of the full adult size listed by Fishbase, so a tad more than 7" in this case.

That said - I think your 100 gallon is going to be pretty crowded when these fish all max out (do you have more than the 5 fish you listed?).

Jay
In my experience many fish slow their growth to a crawl in a smaller tank. It doesn't necessarily mean they only grow to "fit the tank" but it certainly affects their growth rate negatively.

If they slow their growth at 5 inches it would not be too bad, though the larger one is getting close to that

That tank has currently
a pair of Amphiprion bicinctus (plus 3 of their babies)
a pair of Pygoplites diacanthus flavescens
a pair of Calloplesiops altivelis
a pair of Synchiropus splendidus
a pair of Gramma loreto
two Siganus vulpinus
and a single Pseudochromis fridmani
 

mort

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Rabbitfish are renowned for their fast growth. It's unbelievable how fast some of the larger species can grow but they do tend to slow down when the hit a certain size.
 

OrionN

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Tangs will not grow in aquarium to each normal wild size. Also tangs will be smaller in small tank than large tank. This is an indisputable fact. I have plenty of tanks and tangs so keeping them in various size tanks is no stranger to me.
Your Foxface will grow quickly and will be a lot larger than a 5 inch fish by the time their grow slow down, per my experience of my fox face in a 65 gal tank.
I think I tend to feed my herbivores a bit more than you, while you feed more meaty type of food than me. Foxface will get large quicker, and larger end size so than a PBT IMO. If I have to rank how quick and how large of my larger fishes I would rate them as below:
Sailfin tangs>One Spot fox face=Cheveron tang>PBT>Purple Tangs>Yellow tangs+Kole>Tomini=CBB=Regal angels.
I have keep a lot of large fishes in the past but recently I tend to go for smaller fishes that reach aquarium size about the same size as wild caught fish for the species.

Somehow my experiences with my Foxface, both One-spot and Lo, indicated that grew to be large very quickly reach 8 inches in a hurry.
 
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lion king

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Here's my onespot, the smaller variety of the species. He went from 3.5" to 7" in about 3 years. I have seen these guys close to thier natural max in home aquariums. Honestly that's alot of fish for a 100g.

20200923_221138.jpg
 

JumboShrimp

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My Onespot Foxface grew more rapidly than just about any other fish I had— to a good 7” in about a year and a half in a 6’ tank. I feed heavily. (However he mostly hid, so I traded him back to my LFS.)
 

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