How can I tell if a fish has outgrown its tank?

[Perpetual Novice]

I have fish that I know will outgrow my tank. They’re small now as juveniles but I know some reach over a foot when grown. I have plans for where they will go when they do get too large. But I don’t know how to tell when that is. What are the signs that it’s time for a fish to move to one of my larger systems?

 

[Andrew Schubert]

I have fish that I know will outgrow my tank. They’re small now as juveniles but I know some reach over a foot when grown. I have plans for where they will go when they do get too large. But I don’t know how to tell when that is. What are the signs that it’s time for a fish to move to one of my larger systems?

Haven't haff the problem myself... but my first thought would be if starts getting aggressive or seems extra stressed

 

[sarcophytonIndy]

If it can swim from one end to the other in a single motion

 

[nitrodude]

When its tail touches the left side of the tank, while his head touches the right side of the tank, is a pretty good sign you need to upgrade.

 

[ZoWhat]

When fish are unhappy they instinctively go into starvation mode and quit eating. But a lot of time unless you're Johnny-on-the-spot with the transfer, their starvation mode leads to death within days.

Imo I would never buy a fish that I cant potentially cant care for in the future. Reason why I dont own a horse on my 1acre property.

 

[Perpetual Novice]

When fish are unhappy they instinctively go into starvation mode and quit eating. But a lot of time unless you're Johnny-on-the-spot with the transfer, their starvation mode leads to death within days.

Imo I would never buy a fish that I cant potentially cant care for in the future. Reason why I dont own a horse on my 1acre property.

I can still care for it. I have a larger tank it will move to when its ready. but there are other tangs already in tht tank so i want to give it as much time to grow as i can afford it.

 

[ZoWhat]

I can still care for it. I have a larger tank it will move to when its ready. but there are other tangs already in tht tank so i want to give it as much time to grow as i can afford it.

What is this fish?

Your other mature tangs have drawn up territories and when your "grown fish" is ready... the other tangs are going to be unwelcoming to a larger fish with an extra mouth needing to eat.

Theres a balance to consider here. Most success comes from getting all the same aged fish In different species that grow-up together and accept each other presence.

But this all just my opinion

 

[Perpetual Novice]

What is this fish?

Your other mature tangs have drawn up territories and when your "grown fish" is ready... the other tangs are going to be unwelcoming to a larger fish with an extra mouth needing to eat.

Theres a balance to consider here. Most success comes from getting all the same aged fish In different species that grow-up together and accept each other presence.

But this all just my opinion

There are 3 tangs in one tank and two tangs in a smaller tank. In the larger tank a desjardini and powder blue tang are the largest and will have to be moved soon. The sailfin is the largest and is the reason there is peace in the tank. It’s only 100 gallons and she is the gentle master of the tank keeping t he powder blue in check. When she leaves, the powder blue will probably have to move at the same time because I doubt good things will come from a powder blue being the dominant fish. So when the desjardini and powder blue leave, I want to move the two tangs from the smaller tank to the 100 gallon at the same time. So I’m really asking this question on behalf of a lot of different fish. I have it all planned out. I just don’t know when to make the call. Both tanks are peaceful and the fish are showing no signs of stress so I don’t want to disrupt the community unnecessarily.

 

[Timfish]

Keep an eye out for steriotypy behaviour or constant and repetitive behaviour. This will vary by individual, not by species, and the social dynamics in a system will be a factor.

 

[Perpetual Novice]

Keep an eye out for steriotypy behaviour or constant and repetitive behaviour. This will vary by individual, not by species, and the social dynamics in a system will be a factor.

Well, I have seen my desjardini go into a stressed-out fit once. It was bizarre. I was watching some youtube videos about reefing and I noticed my desjardini turned white and was swimming frantically back and forth against the side of the tank. I was immediately concerned and racking my brain for a diagnosis when I noticed my tv was displaying a video focussed on a desjardini in someone's tank with lots of shots of the youtuber's desjardini swimming around. my tank faces my tv about 7 feet away. I turned off the tv and within a minute my desjardini had darkened back to regular hue and was swimming calmly as usual. Do you think it saw the tv and recognized the fish on screen as a threat? or should I take this instance as a red flag that my desjardini is outgrowing the tank? so far this is a one-off incident.

 

[Timfish]

Well, I have seen my desjardini go into a stressed-out fit once . . . Do you think it saw the tv and recognized the fish on screen as a threat? or should I take this instance as a red flag that my desjardini is outgrowing the tank? so far this is a one-off incident.

First off reacting like you described could be for several reasons. Something getting caught in one of it's gill for one example. If it's just a one time or jsut an occasional event I would not worry about rehoming it to a larger system. Steriotypy behaviour is going to be constantly repeated. Your tang can see very well what's going on outside it's tank so it seems reasonable to me it might have been reacting to seeing a tang on your TV. I did an experiement with one of my tangs and standing ~12' away from it's tank it could clearly recognize it's food container from similar sized mugs and glasses reacting excitedly when it's food container was picked up.