Changing mouldy test tubes

Changing mouldy test tubes

I’m often contacted by panicked ant enthusiasts, worried about the appearance of mould in founding chamber test tube set ups.  Fear not! I’m writing this blog post to let you know when it’s time to worry about mould, and how to do a test tube change when it’s needed.

First of all, take a deep breath. It’s OK. Mouldy test tubes aren’t typically an urgent issue, and occasional test tube changes are relatively easy to manage. When deciding when to do a test tube change, I take into account the stress that the queen will experience.  Shifting a young colony from one founding chamber to another is a big deal for a queen, and not something you want to unnecessarily impose on her.  Therefore, I wait until the mould is quite significant before embarking on a test tube change.

Here are some examples of how bad I let the mould get before changing tubes:

Mouldy tubes.jpg

My approach to setting up tubes is low key. I use tap water, because I live in a suburban area with access to treated, clean tap water. If your house only has rain water, I’d recommend boiling or filtering. I highly recommend washing your hands well with soap and water before setting up tubes. Hands are gross!

The amount of mould that accumulates in tubes seems to be associated with the cleaning habits of the species. Pheidole are a notoriously messy bunch, and it’s not unusual for their tubes to have mould issues after only a month or so.  For most species kept in dark, warm conditions, I find three months is pretty average.

Steps for undertaking a test tube change are:

1.       Wash your hands.

2.       Decide which size tube will be best for your colony’s next home. I start smaller species in 16mm test tubes, and transfer them into 20mm tubes when their population grows to the point that it becomes tricky to feed them in the 16mm tube.  Your ants will be most comfortable with minimal territory to patrol and protect, but you obviously don’t want to be contending with escapees at meal times!

3.       Set up a new test tube. See my how-to video here

The new tube should be one third water, plugged with cotton wool.  The cotton wool needs to be fully inserted into the water, so that the ants have access to moisture.  I use a chop stick to push in the cotton wool.  I then wrap the chop stick in a tissue and wipe out the inside of the tube, to make sure it’s not too wet. Excess moisture can be a drowning hazard.

4.       Connect the mouldy old tube to the freshly made new tube. This can be done in several ways:

-          If you’re the kind of ant keeper who loves to have all the cool tools, here at Ants Everything we’ve developed test tube connectors to make changing test tubes very easy. They feature ledges to support the tubes and internal o-rings to cushion the connection. To purchase go to

-          Another option is to use clear PVC tubing. PVC tubing can be found at your local hardware store. Be aware that test tubes are measured with reference to outside diameter, while PVC tubing is labelled with reference to inside diameter. 16mm PVC is perfect for 16mm tubes and 19mm fits over 20mm test tubes – it has a little bit of give in it.

-          If your colony is advanced enough to be attached to an Ant Everything outworld, offering them a new test tube is a simple as connecting the fresh tube to other other end of the outworld! Your outworld would have been supplied with two open grommets and a closed one.  Adding a second tube is as simple as switching out the closed grommet for the open grommet and inserting the new test tube.


 5.       Place something over your newly made test tube to keep it dark and therefore more appealing to your colony. I typically just use a tea towel. Alternatively, you can encase the tube in alfoil or hot water pipe insulation (as shown in the above picture).

6.       Shine a light on the old test tube to encourage the ants to seek out the darkness of the new tube. I use an LED desk lamp, as it doesn’t use much electricity, or get hot.

7.       Be patient!  It’s not unusual for ants to take days to decide to move. It’s also not unusual for them to partly move, and then move back again, before finally deciding to move for good! They’ll get there.