Having a backup tank is a good idea if you want to keep your fish healthy. It can be used as a quarantine, hospital, isolate aggressive fish, separate stressed fish and provide emergency housing.
Quarantine
Even if your new fish appear healthy, they could be latently carrying contagious diseases that could infect the other inhabitants you have in your aquarium. All it takes is one sick fish that could send your aquarium, even if you kept the waters as healthy as possible beforehand, into turmoil. So it is essential that you separate the newcomers from the existing aquatic life that you already have in your existing tank.
Most expert fish keepers like to quarantine fish for at least four weeks. A vast majority will also medicate their new stock as a precaution in order to get rid of any latent diseases.
Hospital
If you see a sick fish, you can also use a backup aquarium as a hospital tank. As we already mentioned above, the ill individual could infect others in your aquarium.
Separating the ailing will not only keep the rest of your population safe (although you should still keep a close eye on your healthy stock to make sure nothing is spreading), it will also make treating easier. Most medicine will harm live plants, so you have to remove them (and keep them alive in another tank) if you decide to treat your main aquarium. If you have a community of different species, some of them may not react well to certain treatments as well.
If your backup tank is smaller, in terms of gallons, then you can also save some cash on medicine. This is because dosing medication is based on water volume.
Jail
A separate tank can also be used as a jail house. An aggressive fish can cause havoc to the rest of the community by attacking other inhabitants, rather if they are nipping fins, chasing away the scared and/or outright killing their tank mates. Both injuries and stress and lead to the onset of certain diseases. By removing the aggressive fish, the rest of the community should feel safer, be healthier and will begin to act more outgoing.
A backup tank will buy you some time when it comes to deciding what you want to do with your aggressive fish. You can give it away to a fish store or another fish keeper, try reintroducing it back to your community or simply let it live in the backup tank.
Safe House
On the other end of the spectrum, a backup can also be used as a safe house. If you see a fish that is scared and is constantly being chased around, especially during feeding time, then it is best to separate it from the rest of the pack.
By keeping the weaker fish in a separate tank, you should be able to relive stress. If the fish still has some room to grow, the extra food it will get (as opposed to being chased off in your main aquarium) will bulk them up. Hopefully, they will get big enough where the other inhabitants will leave them alone if you decide reintroduce the weak fish into the main tank.
Breeding
You can also use a backup tank to breed fish. In order to reproduce, some species require different parameters. If you have a community tank with different fish, then changing the parameters of your main aquarium could end up being detrimental to others. So it is best to use a separate fish tank to prevent harming the rest of the community.
Raising Fry
Not to mention that some fish view eggs and/or baby fish (also known as fry) as food. If you want to hatch the eggs and raise the fry into as appropriate size where they won’t get eaten by others in your main tank, then you should raise them in another aquarium.
By using dedicated baby fish tank, you can also ensure that they are eating the food. In the main tank, all the older fish could gobble everything up before the babies can get something to eat, which will starve the adolescent and eventually kill them.
Emergency
Last but not least, a backup tank is also a good idea to have in case you have an emergency. Your main tank can suddenly start to leak or crack. It may also just completely explode, causing a huge mess all round.
Of course, the first thing any fish keeper should worry about is the health of their fish. If you already have an extra tank nearby, you can easily set up a new home for the inhabitants of your old broken tank. We recommend transferring as much substrate, decor, plants, equipment as possible as they contain beneficial bacteria to remove wastes from the water of your new tank.
Aquarium Alternatives
Of course, you don’t have to use another fish tank as a backup. Just about any container that can hold water will work. With that said, if you want to keep a close eye on the fish, then the clarity provide from an dedicated aquarium may be the most convenient.
Best tank size to use as a backup
The best size for a backup tank depends on the type of fish you are keeping. Since you will most likely keeping them for an extended period of time, it is best to give them the best water quality as possible. As we stated in Aquarium Blueprints’ tank size selection guide, your water parameters will become more stable with bigger volumes.
Recap
A backup tank is useful for quarantining new or sick fish. It can also help separate aggressive/shy fish from the community.
If you want to breed your aquatic pets as well, you most likely need a separate aquarium to entice breeding behavior in addition to keeping the eggs and fry safe from predation. Last but not least, it is also not a bad idea to have a backup ready for emergency.
When it comes to size, the more gallons a tank (or container) can hold, the better the water parameters will be for your fish in your extra tank.