top of page

Ant Formicarium Hydration Guide 

Why is formicarium hydration so important?

This is a critical aspect in the ant-keeping hobby; proper ant formicarium hydration is key to a thriving ant colony. Unfortunately, one of the most common mistakes in the hobby is overwatering your ants! Followed by underwatering your ants! 

This guide will cover how water travels through air and porous materials, different hydration mechanisms and how they work, and general practices for our products.

Our formicaria are classified into; GEN 1, GEN 2, GEN 3, Evaporator module, Test tube and Naturalistic class. Their hydration varies slightly and can be combined in most instances. 

ant formicarium hydration

The basics of water travelling inside a formicarium:

How does water travel inside a formicarium? First, we must understand how water travels within the air and porous surfaces; let's deconstruct some components first.

  • Warm air rises to the top as it is lighter.

  • Moist air rises to the top as it is lighter.

  • Warm water evaporates faster than cold.

  • Warm air can hold more water molecules in suspension than cold.

  • Water travels from higher concentration areas to lower ones; this applies to air and substrate.

  • Relative humidity % changes with temperature (more on this below).

- There are two main types of hydration mechanisms, direct and indirect:

formicarium hydration chamber
  • Direct:

Water is directly in contact with the substrate through porous materials, and it transports water from the chamber into the rest of the formicarium utilizing “capillary flow” (the wicking of water in narrow spaces or pores) and “surface diffusion” (the movement of water molecules through a solid material from higher to lower humidity). KEY POINT: Direct hydration chambers can transport water faster into the substrate than indirect ones and do not depend on factors like temperature or air humidity to transport water. How much water is transported into the substrate is what we control “directly” by adding more or less water to achieve the desired hydration.

  • Indirect:

Water is not directly in contact with the substrate and must transport into it utilizing “vapour diffusion” (air carries water vapour); water evaporates into the air and diffuses from the side with the higher air humidity to the side with the lower amount. Such gets absorbed by hygroscopic materials such as porous substrates (pulling water molecules out of the air) and condensation (air saturated with water vapour or a temperature drop forcing water molecules out of it). KEY POINT: Indirect hydration chambers heavily depend on the air’s temperature and humidity inside and outside the formicarium to transport water. The fluctuations in such values are what we control to “indirectly” achieve the desired hydration; ironically, the amount of water in them does not affect humidity; either there is water or no water available to evaporate.

formicarium with water evaporator module attached

- Air humidity or substrate humidity? What is the difference?

The total amount of water vapour in the air is defined as absolute humidity, and it becomes relative humidity when we consider the temperature of the air; as such determines the dew point (at which we achieve 100% RH).  Hot air is capable of containing more water compared to cold. When air is 100% RH, it cannot absorb more water molecules. If we drop the temperature, water molecules will be forced to exit, precipitate, and condense on surfaces. The opposite happens if we go from cold to hot air, making the air feel dry and dropping the RH %.


Similarly, substrate or porous materials can only hold a maximum amount of water; this mainly depends on the size of pores and quantity within the material’s molecular structure that allows liquid to pass through and be stored. Substrate humidity is relative, and it measures the % of water present compared to the amount needed to get saturated, where no more water can be absorbed, or 100% humidity.


This means we can have a substrate with 75% humidity and the air around it at only 25%…! Or the opposite, very humid air and very dry substrate. It all depends on the temperature and movement of the air.

- Let’s put all of that together:

A direct hydration chamber raises the humidity of the substrate directly; this means water first travels throughout the substrate and then evaporates into the air inside a formicarium; how quickly and how much water the air absorbs depends on its relive humidity and temperature of both air and substrate, but also ventilation inside the nest that could introduce air from outside that may have a different humidity % and temperatures! So water transport happens first on the substrate and then in the air. 


The indirect water chamber first needs to evaporate the water into the air around it; once in the air, it will diffuse and spread inside the formicarium; the substrate will absorb more or less water from the air depending on temperature, hygroscopic coefficient and condensation. So the mechanism is backwards compared to direct; water transport in the air happens first, then substrate. To move more water or faster, we need to heat the hydration chamber to increase evaporation and then keep the substrate or areas that need the water at a lower temperature so when the wet air reaches them; it will be forced to seem more humid and allow for absorption or condensation onto such surfaces.


Inside a formicarium, it is common to have more water in the substrate as it can hold more water than air; the air’s relative humidity will directly depend on the temperature and how much water the substrate or indirect hydration chamber evaporates. This is why we see water droplets on glass surfaces, the substrate absorbs the water quickly, but glass gathers them into droplets, unable to go back into the air. In either case, a wet substrate or glass indicates that the relative humidity at some point reached 100% on either or both, forcing water molecules to exit and condense, saturating the surface and looking to us as “wet.” And this is why; If it looks wet, it is too humid.


This explains why formicarium hydration is a mystery to some; there are many factors present; is water travelling directly or indirectly to its destination? Is the destination the substrate or the air, or both? Do ants need more humid air or more humid substrate? Is one side hotter or colder, and do we need temperature and humidity gradients? Etc.


We often assume the objective of a hydration chamber is to provide ants with drinking water, but that is not the case, as ants mainly acquire clean water from early morning condensation or rain and fluids from their food sources; the substate in their nest is hydrated receives mainly from rainwater that penetrate deep. The main objective instead is to hydrate the air and walls. Like humans in a house, we drink water to stay hydrated, our lungs and skins like 50% relative humidity in the air, and we prefer our clothes and beds to be dry.

Example with Camponotus species:

Camponotus generally do not require much humidity; on top of that, For example, if your house has air with a relative humidity of 50% and temperatures around 24ºC the formicarium will need close to no water, just enough to keep the substrate just slightly moister than the air; for this species, a water evaporator with no heat applied and a few drops of water once every few days in the built-in direct hydration chamber of the nest will be more than enough. In the photo, we have two tubes in an array; the tube on top has water and sits at room temperature, and the second tube was set up dry and is near a heat cable. The queen and eggs are in the wet, colder tube, and the cocoons are in the dry & warmer tube. In nature, multiple species place the queen deep underground and the cocoons closer to the ground under a warm hot rock. 

Camponotus ant colony in test tube with water and dry cotton.

Hybrid Formicarium Hydration Chamber Instructions:

General notes:


  • Always use distilled water; this helps diminish mineral build-up over time.

  • At a minimum, wait at least 24 to 48 hours after the hydration chamber empties before adding more water.

  • If water droplets are present on the glass or substrate, or if it looks wet, do not add more water; even if the water chamber is empty, too much water can cause flooding and mould outbreaks, and such excess will look for ways to escape and evaporate, leaving salts, or mineral build-up behind.

  • Direct hydration chambers must only be filled to the max capacity (100%) on their first use; after initialization, only fill to a % similar or lower to the relative humidity value required by the housed species. 

  • We suggest introducing ants 24 hours after the first fill to allow moisture to settle in the substrate.

  • Indirect hydration chambers such as evaporators can be filled to the max at all times as they are mainly controlled by temperature.

- GEN 1, 2 & 3 formicaria:

The three generations work with a direct hydration chamber found inside the formicarium. As explained above, direct hydration chambers can transfer lots of water and do so quickly. The substrate is contained inside a glass & plastic frame and requires very little water to stay humid. The amount of water added to the hydration chamber and the frequency determines how much water the substrate absorbs and, consequently, how humid the air inside will be.


In all three generations, the goal is to create a hydration routine & schedule, for example, “1mL of distilled water every five to six days”. The temperature, ventilation and humidity around the formicarium determine how fast this water escapes; we want to add just enough to keep a balance around the moisture needed in the substrate; water added vs water evaporated vs required humidity. It is best to offer small amounts of water periodically compared to a considerable amount every so often. The amount and frequency will differ for all users and requires observation, experimentation and fine-tuning; most users quickly learn to recognize the subtle cues, especially if the general notes in this guide are followed.

Always inspect the glass and substrate surfaces for condensation or signs of wetness; having some minor condensation early in the mornings is typical (or with any drop in temperature), but if it is always there or it takes longer to disappear as the day warms up, this means you need to add less water and less often. On the contrary, if you never see condensation even with aggressive reductions in temperature, then you may need to add more water or do so more often; you can DIY test how far you are from the DEW point with a tiny piece of ice or a chilled coin, place it against the glass on the area you want to test, pay attention to the times it takes for light fo on the glass to appear on the inside, remove and pay attention how long it takes for it to re-evaporate.


If the hydration chamber is empty, does that mean the formicarium is dry?

No, water may disappear from the reservoir, but it is now stored within the nest’s walls in the porous substrate and will slowly evaporate through the plastic frame and glass. But, if left enough without water, the substrate will eventually dry out; this explains why a routine and schedule are the best for ensuring consistent humidity.


Radiant heat coming from above is generally preferred (heat lamp or light bulb, heat cable on the glass); it mimics the sun warming up the ground and objects like rocks; in this case, glass tends to warm up instead of the substrate, avoiding the typical condensation we get on the glass when heating from underneath with a cable or heat mat (in this case glass is colder).


When it comes to hydration, the differences between the GENs are:


  • GEN 1: has a sealed hydration chamber, a glass is glued in place, and water can only be transported onto the substrate through the porous material next to it. This is why the honeycell, honeycell mini and classic hybrid can stand or be tilted.


  • GEN 2: has an unsealed hydration chamber directly under the glass that covers the entire formicarium, water is mainly transported onto the substrate throughout the porous material, but capillarity and evaporation can also happen on the tiny gap between the glass and plastic frame.

formicarium humidity
  • GEN 3: the water chamber is sealed and enclosed in the frame (not visible); water can only be transported onto the substrate through the porous material next to it. The hydration chambers hold less water than GEN 1 & 2 and are located at the bottom of the design under the substrate. GEN 3 relies on visual inspection of the substrate, changing from light to dark grey as humidity distributes through the inside walls. Using this gentle change in colour, you can determine when the formicarium is starting to dry again and, at such time, add a small amount of water. 

- The Evaporator module:

The evaporator module uses indirect hydration. It provides water vapour through a mesh-protected tube port. The evaporator module is sensitive to heat; the hotter it is, the more water evaporates and diffuses into the formicarium air. A heating cable can be placed between the formicarium and the watering module, a heat mat under it, or a radiant source like a heat lamp can be pointed towards the glass bottle to increase the temperature in that area.


It is widespread to see formicaria with a little water reservoir covered with a metal mesh to prevent ants from directly touching water; such is an indirect hydration mechanism relying on water evaporation. To saturate the substrate, the air must reach 100% RH to condensate onto the substrate. Refill the bottle as often as needed.

water evaporator module attached to a formicarium
water evaporator module for formicarium or ant farm

Our water evaporator module can be purchased independently and connected to any GEN 1, 2 or 3 formicarium to allow for direct hydration strategies. The curvesome formicarium revolves around this idea; this method allows controlling the relative humidity of the substrate with the direct hydration chamber and the relative humidity of air through the evaporator as needed.

- Test Tubes:

Refillable and traditional test tube setups rely on the direct hydration chamber mechanism; water travels through the cotton and evaporates into the air inside the tube. There is little that can be done to control the relative humidity of the air inside other than changing temperature, creating a gradient with a heat source or reducing the opening at the front of the tube to reduce the amount of water that escapes.



  • If you place the water reservoir and wet cotton on top of a heat mat or cable, such will evaporate more water; if the front of the tube is not being heated, a gradient from cold to hot will form, this will result in condensation forming on the glass as the air inside becomes very humid and condenses on the cold glass surfaces.

  • If you place the heating cable on the front of the tube, such will heat the air lowering the relative humidity and increasing the amount of water that escapes through the front cotton, unless the entrance is very restricted.

  • Using a heat lamp from above or placing the heating cable above the tube on the air side near the wet cotton will prevent water from condensing on the glass and evaporate water from the back, creating a warm, moist environment.


There are many combinations, and each will fit different species depending on the humidity needs.

ant test tube with refillable water feature

Refillable test tubes, when to add more water?

Wet cotton looks different from dry cotton as it interacts with the glass. Wet cotton looks flushed as water fills the air gaps between the cotton fibres and the smooth glass surface; dry cotton seems to separate from the glass as these air gaps reappear. In general, 1mL of water seems to last 2 to 3 weeks.


Remember, less is more…!

- Naturalistic Formicaria:

These setups usually don't have a dedicated hydration chamber; they rely on the soil mix used to absorb, diffuse and retain water; in that sense, they work with a direct hydration approach; in practice, water is added through hydration ports that bring the water directly to the soil, and the colour or apparent wetness of the media is used as an indicator for how much water is needed.


It is wise to supply water slowly to avoid erosion or collapse of tunnels as water diffuses; a very dry substrate is also more prone to collapse with vibrations. Please remember that the quantity of soil or tunnelling media present directly affects how often and how much water to add; a small volume of media can dry faster and requires water more often in small amounts as it can hold less water, a large volume can long later and buffer humidity better and can hold more significant amounts of water. Materials like vermiculite, perlite or coconut fibres are often added to the mix to help with water retention and absorption. 

bottom of page