WARNING: This will be another of my usual essay type posts, for those who want to skip!
My previous set up, and my current set up/plans for hospital/quarantine/nursery/temporary holding tanks (which are different things, as Byron said, and need different considerations!) in case this answers any of your questions, or you pick up any tips.
For a long time I used a proper glass 12 gallon tank as a quarantine tank, a hospital tank and a grow out/nursery tank, at different times. Personally I don't love having a permanent tank set up for myself; unless you're going to be doing a lot of quarantining of new fish, or you're breeding fish and need a separate tank to raise fry. Then it's worth having a proper tank set up all the time. Now that I don't breed livebearers anymore, I've got rid of that tank, and use a food-safe plastic tote, that I can turn into a 'cycled' temporary tank in about 30 mins, as
@Bruce Leyland-Jones does.
Whether a fish is sick or new fish are going to be quarantined for a while - after going through the stress of being shipped, in a store tank, then moved to your quarantine - you have to think of how best to make the environment as comfortable and stress free for the fish as possible; while also being able to observe and medicate the fish if needed. So things like substrate, hiding places like decor, hardscape and plants -especially floating plants that make fish feel safer from predation while helping with water quality - can really help, and are essential to my mind. But they also need to be items you can either sterilise after use, or don't mind disposing of, should the new/sick fish have a disease that you really don't want to transfer to a main tank. So don't use a favourite piece of wood, or expensive substrate and plants you want to keep!
Water quality is of course important. Most of my main tanks have two filters, along with heavy live planting. I do this to keep the water as pristine as possible, but also because I can easily pinch a sponge filter from one of those tanks to set up a quarantine tank at any time, without having to keep it running and cycled on a permanent quarantine tank, and the second filter plus plants in my main tanks means they're fine even when I take the sponge filter out. You need to be doing frequent water changes whether fish are sick or in quarantine, and also because while this tank may be somewhat "cycled", it is still not a fully
established, stable tank. Cycled and established are very different things.
That sponge filter from an
established tank is then basically used as a seeded cycle for the new, temporary set up. I use a food-safe tote like this;
View attachment 143019
Just for fish-stuff. When not in use, it holds spare decor, extra heater (with heater guard, so it doesn't melt the plastic when rested on some stones!) and when half filled with water it holds 20 gallons. Plenty for my needs, and also not a huge amount of water to medicate if needed. When needed I set it up on top of a dark surface, so the fish have the sense of a substrate (bare bottom tanks can sometimes cause stress), or can add some spare gravel or sand that I don't mind binning afterwards.
I add the heater with guard, the stolen sponge filter, and an airstone. There, temporary set up ready for fish!
(can also be used as a breeding tank, for when you want to breed some fish and save the eggs that wouldn't otherwise make it if the fish were bred in the main tank).
I have some spare decor I no longer use stored away - small stones, small pieces of wood from old scapes, cheesy "no fishing" ornaments I was gifted but would never put in my main tanks -and silk plants I bought from the "reduced, clearing stock" bargain bin at the LFS
Most of that stuff except for the wood and stones can be sterilised in a mild bleach solution after use, then stored for next time.
I take cuttings from plants in my main tanks to add to the quarantine tote. All stuff that I don't mind throwing away after use; because I don't want to lose my expensive, slow growing plants, and I don't want to risk putting anything from quarantine back into my main tanks. Fast growing stem plants like elodea, l.sessiliflora, water wisteria etc are perfect for this, and floating plants produce enough spares that I need to throw away handfuls of the stuff - so there's always plenty to spare for quarantine when needed.
This way I don't need to worry about keeping a spare set up cycled between use, or the temptation to turn a proper tank into another display tank! It has enough space, equipment, live plants and low lighting for fish to feel secure and de-stress. Enough water volume that with water changes, ammonia spikes aren't a concern the way they would be in a three gallon, and I can whip it out and put it anywhere when needed, and not have it taking up space while not looking terribly pretty when not in use.
