Tank volume v capacity to determine fish

[Mariette]

When considering the types of fish you can keep in a specific aquarium, do you consider the volume or capacity of the DT? In particular, I’m considering a 130g tank w the capacity to hold 110g. 20g lost to the overflow box and the water level being kept an inch below top of tank.

So, let’s say I want a fish that’s generally approved for a 125g tank. Would I be able to keep it in the tank I’m considering?

 

[WVNed]

Yes
assuming you have a commonly available tank and not one of the oddly shaped ones you see on here at times

Tank sizes for fish are loose recommendations. They can be stretched a bit. They are typically based on how much room a fish requires at adult size to swim or forage for food.
You dont want a fish that can grow to a foot long kept in a 2-3 foot long tank.

 

[SDK]

Volume yes, but also width as well. Most standard 125 gallon tanks are 6’ long, so that may be a factor if you are looking at a 4’ wide tank.

 

[SDK]

Yes
assuming you have a commonly available tank and not one of the oddly shaped ones you see on here at times

Tank sizes for fish are loose recommendations. They can be stretched a bit. They are typically based on how much room a fish requires at adult size to swim or forage for food.
You dont want a fish that can grow to a foot long kept in a 2-3 foot long tank.

Beat me by ten seconds lol

 

[Mariette]

Yes
assuming you have a commonly available tank and not one of the oddly shaped ones you see on here at times

Tank sizes for fish are loose recommendations. They can be stretched a bit. They are typically based on how much room a fish requires at adult size to swim or forage for food.
You dont want a fish that can grow to a foot long kept in a 2-3 foot long tank.

That makes sense. Thx

 

[Mariette]

Volume yes, but also width as well. Most standard 125 gallon tanks are 6’ long, so that may be a factor if you are looking at a 4’ wide tank.

Good point. Didn’t know the standard 125g was 6 feet. One I’m looking at is 5. So something to keep in mind when choosing fish.

 

[SDK]

Good point. Didn’t know the standard 125g was 6 feet. One I’m looking at is 5. So something to keep in mind when choosing fish.

Five feet is definitely better than four for fish that like to roam. I would feel pretty comfortable putting a fish recommended for a 125 into a 5’ long, 130 gallon tank.

 

[WVNed]

As would I

 

[Mariette]

Five feet is definitely better than four for fish that like to roam. I would feel pretty comfortable putting a fish recommended for a 125 into a 5’ long, 130 gallon tank.

Really? Awesome

 

[Mariette]

As would I

Excellent thank you

 

[norfolkgarden]

Jealous! Lol, 125 is future goal.
Hope you have a great time with it!

What fish are you planning on stocking?

 

[nereefpat]

Yes, what fish?

It's a good point that a lot of tank size recommendations are based on standard tank sizes: 40, 75, 125, 180...and so on.

 

[Nathan Milender]

I think you have a few things to consider and I generally find that the charts and loose guides rarely give insight on these issues.
1) How much bioload does the fish require? A super energetic 3 inch angel is worth a lot more bioload than a 3 inch watchman goby.
2) Does the fish have specific behaviors that require more space? A constant swimmer may need a specific length to turn around in that some volumes will not accommodate even if high volume.
3) Compatibility. If the fish are aggressive/semi aggressive, is there enough distance to allow them to blow off steam or hide? Can everybody eat together or is one pig going to make sure to get it all?

An octopus has high demand on all three for example and would generally be the only thing in there that is not octopus food.

I think most of this is overcome by slow stocking a few at a time and seeing how they settle and adapt to change. To be fair, I am still generally novice at this and there are plenty of fish I have not had or killed. This is the approach I use and when I add a new fish this is what I consider. Sometimes, no matter what I read, the fish does not do what it is supposed to so I like to err on the less fish side.

 

[Mariette]

Jealous! Lol, 125 is future goal.
Hope you have a great time with it!

What fish are you planning on stocking?

Hahahaha hang in there. I’ve had a 55g freshwater for 2 years that I’ve been using as a saltwater. Patience.

Not sure yet. Definitely want a tang for sure. Have to look into mixing some together. If I decide to go no coral, maybe a regal angelfish. So much to learn and consider

 

[jsvand5]

Hahahaha hang in there. I’ve had a 55g freshwater for 2 years that I’ve been using as a saltwater. Patience.

Not sure yet. Definitely want a tang for sure. Have to look into mixing some together. If I decide to go no coral, maybe a regal angelfish. So much to learn and consider

If you are thinking of a 125g, you might as well just go for a 180g. Cost difference isn’t very significant and the extra size is a big plus.

 

[Mariette]

I think you have a few things to consider and I generally find that the charts and loose guides rarely give insight on these issues.
1) How much bioload does the fish require? A super energetic 3 inch angel is worth a lot more bioload than a 3 inch watchman goby.
2) Does the fish have specific behaviors that require more space? A constant swimmer may need a specific length to turn around in that some volumes will not accommodate even if high volume.
3) Compatibility. If the fish are aggressive/semi aggressive, is there enough distance to allow them to blow off steam or hide? Can everybody eat together or is one pig going to make sure to get it all?

An octopus has high demand on all three for example and would generally be the only thing in there that is not octopus food.

I think most of this is overcome by slow stocking a few at a time and seeing how they settle and adapt to change. To be fair, I am still generally novice at this and there are plenty of fish I have not had or killed. This is the approach I use and when I add a new fish this is what I consider. Sometimes, no matter what I read, the fish does not do what it is supposed to so I like to err on the less fish side.

Very well put. I always keep in the back of my mind the fact that they’re guidelines and not rules. I like to have a stock list in mind including order before where possible. I’ve got a 55g that I’ll be using as qt and can introduce more than 1 at a time if I can house them together comfortably in qt for an extended period of time. TONS to consider. Also have to account for individuality within species. If u get a usually timid fish that’s actually a jerk, i would have to alter my list accordingly. So some things are wait and see but I like to do as much research in advance as possible because, knowing me, if I get one that’s being a real jerk, I’m very unlikely to rehome it. Knowing me, I’d be buying another tank lol

 

[Mariette]

If you are thinking of a 125g, you might as well just go for a 180g. Cost difference isn’t very significant and the extra size is a big plus.

Hahaha I like the way you think. It’s a space issue to be honest. Maybe it’s time for a bigger house lol

 

[ca1ore]

FWIW, most tank volumes are calculated from the external measurement, not the internal ones. So even before subtracting for things like overflows and water levels you're already down.

 

[Nathan Milender]

I agree with this. Take a look at where the tank is going to go. Whatever length your are willing to accommodate add depth and height and I doubt you will miss the lost room. I have a 6ft 125, if I was not so lazy I would keep all my same expensive gear and up this to a 6ft 250, or maybe just a 1000 gallon whole wall tank.

 

[Jesterrace]

When considering the types of fish you can keep in a specific aquarium, do you consider the volume or capacity of the DT? In particular, I’m considering a 130g tank w the capacity to hold 110g. 20g lost to the overflow box and the water level being kept an inch below top of tank.

So, let’s say I want a fish that’s generally approved for a 125g tank. Would I be able to keep it in the tank I’m considering?

Neither. I go by the dimensions over anything else. Big difference between say a standard 125 gallon tank vs a 150 gallon that is 4 feet long, 2 feet wide and 30 inches tall. The 6 foot long 125 gallon has far more useable space being a 6 foot long tank and doesn't have the headaches of being a tall tank so to speak. Yes water volume matters to an extent, but if you have a 75 gallon display tank and a 210 gallon sump you still only have the useable space of a 75 gallon tank in terms of stocking options for fish.