It’s good practice to quarantine any new additions to your fish tank to help minimise the risk of the newcomers passing on diseases or parasites to your established stock. As well as quarantining new purchases, you may sometimes need to remove fish from the main tank to a hospital tank for treatment in the case of illness or injury.
Why quarantine your new fish?
Fish shops sometimes use UV systems to help keep disease to a minimum, so problems may not show in the shop but may manifest when you get your new fish home. Some shops use large centralised filter systems which means all the tanks are sharing the same filter, so if one tank has a problem there is a risk that it may pass to all of them. Some shops may medicate as a matter of routine to try and catch any problems before the fish are sold, but there’s still a chance that fish may come down with something soon after purchase.
Stress is a major cause of fish disease as it lowers their immune systems and makes them susceptible to problems. The stress of being packed up to travel from the supplier and/or the wholesaler, then the stress of the journey to the shop, then being unpacked at the shop, then being caught and packed up again when purchased, then being plopped into a new tank with unfamiliar tank mates and surroundings – all this stress can take its toll on even the strongest of individuals. Care is needed when introducing a new fish to your tank to avoid it passing disease or parasites to your current fish.
Recommended quarantine periods vary, keeping new fish separate for as long as four to six weeks is good practice. This may sound like an awfully long time to wait, and naturally you’ll be keen to get your newbies into their new home as soon as possible, but a few weeks’ wait is a small price to pay to minimise the risk of wiping out your entire stock.
Why treat your fish in a hospital tank?
There are many reasons why you may need to take a fish out of your main tank and treat it separately. Certain species of fish e.g. clown loaches, as well as inverts, can be very sensitive to medications. If you have a mix of fish and the sensitive ones are in good health then you may wish to remove the affected ones to another tank, or remove the healthy ones if they are in the minority. Medicating healthy fish isn’t recommended as medications can be quite a risk. Medications are designed to be used only when needed with the risk of using them being outweighed by the benefits. It’s much more economical to treat smaller bodies of water as some medications can be quite expensive. Any further problems will be contained and your healthy fish in your main tank will be safe.
Bear in mind that some diseases/parasites will require whole tank treatment so whether or not to hospitalise or exclude any fish from treatment depends on what is being treated. Check out the guides to fish health linked to in the further reading section for more information on various illnesses.
A note on filter media and water quality in quarantine and hospital tanks
If you need to quarantine or treat a fish but haven’t got your spare filter media ready yet, don’t despair. You can take some out of your main filter and put that in your spare filter. Ceramic media can be used in place of sponges in many models, or you could cut a bit off your main sponge, or remove the filter floss and use that in your spare filter.
It’s important to check water quality in a quarantine or hospital tank frequently. If your spare filter isn’t coping you may need to take additional action to make the water safe for your fish such as more mature filter media, increased water changes or use of a chemical water treatment to neutralise any pollutants in an emergency. Quarantining or hospitalising fish in water which is polluted could easily make them much more unwell, or worse.
But I don’t have a spare tank!
Not everyone has a spare tank, or wants to keep a spare aquarium running all the time only to be used infrequently. It takes up space and can be expensive to buy and run.
Jeroen Wijnands takes us through his solution to the problem. The sizes suggested below assume you’ll have small to medium sized fish; if you have larger fish you can still use the same method but will need to get a larger container, filter and heater.
Setting up a quarantine or hospital tank on a budget, by Jeroen Wijnands
Here’s my solution for a quarantine tank on a low budget which also takes up very little space when not in use. It can be up and running in twenty minutes when needed.
A good and sturdy storage box of about 45 litres. And yes sturdy, water weighs a lot and exerts pressure on all sides of the box. Thin plastic may not stand up to these pressures. There’s two that we know that work but there might be others.
1. The Really Useful Box range. You can buy these at various stores, prices vary depending on size and lids are available for all sizes
2. The Ikea Samla box (holds 45 litres) approx £5 and lid approx £1.50
Superfish Nano Heater 50 Watt – approx £11
Superfish Aqua-Flow 50 filter – approx £10
Heater guard/holder with suckers to attach the heater to the side of the box
Other manufacturers also make filters and heaters suitable for a quarantine or hospital tank, these are just suggestions so you have an idea what to look for.
How to prepare your quarantine tank
Rinse out the box well with water with a dash of water conditioner. Leave standing around filled for twenty-four hours to ensure it’s water tight. Put the filter in to ensure it’s working properly and you know to stick it in in a hurry and how to tune the flow.
Stick in the heater, switch it on, and let it sit for three hours. Get your thermometer out and calibrate the heater so that you know the deviation of the one you bought and how to set it to an appropriate temp for your most common stock (probably around 24c). Many heaters have slightly inaccurate thermostats, so if you know how much it’s ‘off’ by you can adjust accordingly.
The next day, once you’re confident that the box wont leak, and that your filter and heater and working properly you can unplug the heater, let it cool down and store it. Take apart the filter and store the sponge somewhere. The sponge of the filter lives in my external but if you don’t have an external filter you can store it out of sight in an area of the tank with good flow, it will still grow some bacteria. Alternatively, you can keep the filter in the main tank if you have room. If you’ve got a few spare pebbles or plastic plants etc. then rinse well and store in a bag next to the box.
When not in use the box sits under a similar one which I use for aquarium supplies.
How I use it my quarantine/hospital tank
When it’s needed I fill the quarantine tank with water from the main tank so acclimatisation is not needed. I decorate as needed, usually just a few pebbles and some left over plants or plastic plants. The gravel in this picture was because I kept some young ancistrus in there.
Quarantine tank: Keep the newly purchased fish in the tank for six weeks before moving them to the main tank.
Hospital tank: If using as a hospital tank, treat the disease with your chosen remedy and follow the instructions exactly. When symptoms have cleared wait another six weeks until returning the fish to your main tank.
After use (and especially if used to treat a disease) the tank can be rinsed out with brine or even a mild bleach solution eg Milton and left out to dry for a week. The sponge can be boiled or thrown out, they’re not expensive, but do remember to get a new one ready. The stones can be boiled or bleached as well and the live plants are also thrown out.
The importance of quarantine (fishkeeping.co.uk)
Fish health: various guides to common diseases and parasites (fishtanksandponds.co.uk)
A-Z of Fish Health: Part 1, A-E (Practical Fishkeeping)
A-Z of Fish Health: Part 2, F-L (Practical FIshkeeping)
A-Z of Fish Health: Part 3, M-R (Practical Fishkeeping)
A-Z of Fish Health: Part 4, S-Z (Practical Fishkeeping)
Find a fish vet (OATA)