The Isolation tank and its uses

Hospital tank” “ Quarantine tank”

The isolation tank is a very important tool for any fish keeper its use can be very effective in the fight against disease. Providing a cost effective way of treatment. It is a must before introducing stock from an unknown or suspect source.

There are those who would use it on every occasion and those who would only use it occasionally but no matter how new to the hobby you are or if you are an old hand, it is something that will be of use and will pay for itself over and over again!

What is an Isolation Tank

The isolation tank is your best defence against disease, it allows you to quarantine and treat infected fish while reducing the risk of other fish been contaminated and reduces the cost of treatment.


When to use an Isolation Tank

  1. The isolation tank should be used before in introducing new stock. This allows the stock to rest and helps avoid stress caused by new tank mates and also and most importantly it allows any symptoms of disease to show before adding the new fish to your tank, thus avoiding the cost of treating the whole tank! And it protects your current stock from the risks associated. You should allow new stock a period of 28 days in the isolation tank and then if there are no signs of disease, introduce the new stock to your tank.


  3. At the first signs of disease or unknown stress remove a fish to the isolation tank. Allow the fish to settle and try to pinpoint the problem, it could be something simple e.g. a tank mate has become too aggressive or the early stages of disease. By isolating the fish you may prevent the spread of the disease and again reduce the cost of treatment.


  5. Sometimes you can not avoid having to treat the whole tank but this in itself may bring up a new problem e.g. the introduction of a new plant has also brought some snails and the treatment for snails can be toxic to some species of fish, thus these must be placed in an isolation tank for the duration of treatment and until the medication has been totally removed so that you avoid any unnecessary lose that would be related to the medication.


The isolation tank is a very versatile tool, its a hospital , a treatment centre or an observation tank. It can be used to prepare a female for breeding, so that you only feed the female or preparing fish for benching(shows) by reducing the risk of damage from tank mates and I am sure you will in time find many more other short term uses for it.

Emergency what do I do?

I don't have an isolation tank what can I do! Its simple, just be creative and look in your presses! There are some simple rules you can use to determine if an object can be used as an isolation tank.

  1. The object should be see through, so you can observe the fish from all angles but if not available any water type container will do.

  2. The mouth of the object should allow all the water surface area be open to air

  3. The object should hold the fish safely and allow it space to move safely and without stressing it.

  4. The object should be six times the length of the fish in question and four times the width (this is preferred but not an unbreakable rule) If in doubt apply this rule as the absolute minimum, 24 square inches of water surface per 1 inch of fish length.

  5. It does need a filter but for the short term do daily water changes. Just remember each water change reduces the medication thus you have to add more so unfortunately this will only increase the cost for you. Avoid the cost by having a spare filter.

  6. Filters in your isolation tank should have the charcoal removed and any other medium that will remove your medication treating the medium is waste and may result in the loss of stock unnecessarily.

Choosing a suitable isolation tank for you!

The minimum size for an isolation tank is what??? Well, that depends on what fish you keep! A tank suitable for a Corydoradinae will not suit a Plecostomus and simply because of the very obvious size difference.

So will I have to spend hundreds of Euro on a new tank??? No, this is not a show tank, it will hopefully only be needed occasionally, and if you're really lucky, never so it can be as basic as possible - lid, filter and a heater if required.

The tank size should be just big enough to hold your biggest fully grown fish comfortably, without stressing it more or confining it.

Do I need an isolation tank?

That is a question, only you can answer! But things to consider are:

  1. Can I afford to treat a tank the size of my current one?

  2. Can I afford to run the risk of losing all my stock and then the cost of replacing them?

  3. Where will I keep the fish that the medication might kill?

  4. Have you more than two tanks?

  5. Do I really want to have to add new stock to my tank without a quarantining time first?


When you consider the above five questions this should tell you if you need to get an isolation tank. There are those who would say it is essential and there are others that say it is not worth the cost. You will not need an isolation tank at first but as your interest grows so will your need for one.

My advice is simple, get an isolation tank sooner rather than later as it is better to have it and not need it than to need it and not have it.

Name: Michael Wallace

User Name:


E mail: This email address is being protected from spambots. You need JavaScript enabled to view it.