Grow out concept

I use several grow out tanks...... Tanks that are used to grow the little minnow sized Characins up to the point where they won't be eaten by other stuff.

These smaller tanks are important when trying to make typically intolerant fish tolerant of tank mates. Put some predatory Characins in large tanks and immediately they start trying to establish territory, move them to a smaller tank where there's nothing to "establish" and they no longer fight.

With all the different growth rates out there it would be VERY difficult if not impossible to mix some of the stuff in my tanks......

Most of the time people are running several tanks...... A "big" tank and the smaller ones are "grow outs"

I keep pups in a 40b until they are off blackworms and onto chopped crawlers. It only takes about a month so I wouldn't consider it a grow out tank, yet I have still gotten guff for it even though its connected to another 400g smhlol. I have been considering adding a 180 as a grow out tank for pups. This will give me more room overall and provide plenty of space for younger, smaller rays until they are sold or large enough to fight the big rays for food. I don't see how this could stunt them considering, under someone else's ownership, my large retic female grew to 12+ inches in a tank no bigger than a 55g with little more than a few worms a week. This obviously stunted her growth but not by much.
With cichlids, grow out tanks are obviously necessary if you want fry or juvies to survive.

I completely agree with you Toby, i've never understood the idea of keeping things in smaller tanks.

There are several logics to follow i think, one being a smaller fish requires a smaller tank allowing for the fish house or area which houses the tanks can accomodate more tanks, personally this has always been flawed for myself because i've never wanted to grow so many fish at one time.

Another logic, which i must admit can be true to a degree is the security the fish gains from being in a small fishtank, personally i actually have two examples of this right now - i have two 6 x 2 x 2 grow outs, in one young juvenile cichla, they are terrified if i enter the room and hide up the corner (my friend with the same fish in a smaller tank has no issues), to feed i have to add the food, sit down, not move and then they come out - in my ray pup tank this logic isn't effective, they are quite happy having the space and don't freak out.

As mentioned above not allowing them the area to dominate until they're more social, although personally i have found the opposite, for instance my 20" + Aimara lives comfortably in my 750G with other fish smaller and larger than himself - i would never dare to put him in a 180G and expect him to accept something else, because there is too little space to provide different territories - i appreciate DB Junkie you are directing your post at young juvenile fish and training them to be socially accepting.

Ultimately, my overall take on it is, the fish i buy small are because i can't buy them large, in which case i accept to have that fish i have to grow it whether that be due to rarety of large sizes or issues with shipping large fish - therefore my objective is to grow that fish quickly and as such i would house it in as large a tank as possible, feed as often as possible and water change more than required.

I also appreciate your comment Toby about it just being here say about upgrading later to justify keeping the fish now, i adopted this attitude in my more ammateur days of fish keeping just to give permission to myself i guess to keep larger predators even though knowing i couldn't do so forever.

As you mentioned though, selling large fish or rehoming in public aquaria is becoming more frowned upon in the UK.

Something else that i'm mindful of is larger fish tend to stress very easily, if i can house a fish in a tank and know i never have to move that fish or enter its tank with a fish net again i rest easier, i hate seeing the distress i cause when a fish is content in its environment and has to be shifted.

in some cases, such as gar, smaller tanks for growing out are recommended so as to prevent them from building up too much speed if they panic, thus lessening the chance of them ramming the glass and breaking their backs, etc.

in some areas of europe where space is at a premium living-wise (denmark, germany, UK, etc) i could see just keeping the one larger tank than housing multiple tanks at once.

in north america, the living space is more accommodating for those of us with tons of tanks on the go, with the ability to use them at different intervals/stages of a fish's lifecycle, to work on giving it the best chance of survival than hoping it doesn't get bullied/gobbled up by something much larger or more fierce.