The scientific name is taxiphyllum barbieri, but it’s commonly called Java Moss. (There are a few older names for it, like vesicularia dubyana, but t. barbieri is now the accepted name.)
Java moss has little, delicate, branching green stems with very tiny, oval leaves. It usually grows between 3 – 10cm thick, depending on tank conditions.
But here’s the kicker: It’s one of the best plants for beginners, and is nearly impossible to actually kill.
It can be dark or bright green, depending on recent new growth. When growing above water, t. barbieri will produce much larger leaves to capitalize on the CO2 available in air.
Like other mosses, Java moss has no root system. Instead, it spreads via rhizoids — brown, hairy, filament-like structures. (Rhizoids are also what give Java Moss its famous capacity to “grip” the surface it’s growing on.)
Ideal Conditions for Java Moss
As with (almost) any other aquatic plant, CO2 and high light will cause java moss to grow faster.
But, here’s the deal: you don’t need it.
This plant is likely impossible for you to kill. It doesn’t even need planting — it will quite happily grow free-floating.
Technically Java Moss does need light. However, any light at all will suffice. Any decent aquarium light is very adequate. Of course, higher light will push faster growth.
It gets even better: Java Moss also doesn’t require a heater. It will survive in temperatures ranging as low as 65º F, and up to 86º. (18 – 30º C) It’s worth noting that t. barbieri grows faster in cooler temperatures, so if you’re looking for fast growth, leave the heater out! (Just a note here that if you have other plants that do require relatively-hotter temperatures, Java Moss will be perfectly fine at higher temperatures, it just won’t grow quite as quickly.)
It is important to trim it properly — as it grows thicker, the interior portions of the plant can be cutoff from light and the flow of water. Of course, all plants need light of some sort, so if that happens, it’ll turn brown as it dies, and it can even cause the entire plant to lose its ‘grip’ on its surface.
A note on flow
Java Moss has a tendency to get so dense that it can block the flow of water through interior portions of the plant. Since plants can’t move to reach nutrients, a lack of flow reduces (or eliminates) the supply of nutrients, and that portion of the plant can easily die. It’s critical the you periodically trim the plant to ensure it doesn’t get overly-bushy.
As with all mosses, algae commonly grows on it. This is even more prevalent in slow-growth conditions (low light/flow/nutrients). To ensure optimal growth, gently agitate the stems during cleaning to prevent any buildup.
Propagating Java Moss could not be easier. Literally cut off a portion of the stems, and leave them floating. Those stems will continue growing without any issues! (Be warned: it can take over your tank if you leave bits floating around!) If you’re going for that natural look, it’ll even survive being put through a light cycle in a blender to cut it into fine, small pieces. This ‘paste’ of Java Moss can be glued or otherwise-bound to hardscape for a very fast naturally-growing look.
And it gets better: having a ton of t. barbieri in your tank will pull a significant amount of nitrates from your water, increasing the time between required water changes.
Java Moss is so good at removing nitrates you’ll want to ensure you’re dosing ferts, if you have other slow-growing plants in your tank, like Anubias.
This plant has no conflicts — it’s great for shrimp tanks, fish tanks, and everything in between. (Fry love this stuff.) Remember, though it grows fastest at cooler temperatures, it’s also able to survive in a wide range. That means it’s compatible with most-any other flora or fauna species in freshwater tanks.
It’s especially good for those attempting to breed fish, shrimp, or anything else. Infusoria grow abundantly on Java Moss — among the most effective ‘first foods’ for any aquatic organism.
Common Problems with Java Moss
I have brown or unhealthy sections of my java moss.
If the plant is thick, ensure that the thick outer portions aren’t blocking light or cutting off water flow to interior areas of the plant. Water flow through the entire plant mass is critical to ensuring the plant stays attached and healthy.
If your Java Moss is new to your tank, it’s expected to have a portion of it “die back” as it acclimates to new water parameters. (Though this isn’t required—proper husbandry can prevent this dieback period.)
If your tank has warmer temperatures (above ~78º F/25ºC), Java Moss will grow at a reduced rate, and can struggle if it was previously in cooler water.
My Java Moss is thin, or not getting thicker.
“Slow growth conditions” (i.e. low/no light, low nutrients, low flow) will result in little to no new growth in Java Moss. If you’re able, try lowering your light to increase the light intensity that the moss receives. Check your water parameters to ensure you don’t have unexpected values, and that there are nutrients available for it to grow. (A bare tank with no fish — an extreme example — will result in almost any plant dying.) Also check the most common issue with Java Moss, below:
My Java Moss has algae growing on it.
In tanks with low (or no) water flow through/around the moss, algae will build up on the surface of the plant. When it’s left on there, it will slowly choke out the moss, blocking light and water. It’s best to maintain moss on a weekly basis, gently agitating its stems to prevent algae buildup. (Once algae is allowed to stay on Java Moss, it’s very, very challenging to separate it from the plant itself.)
How do I save my dying Java moss?
Bluntly: Java Moss is actually really hard to outright kill. Typically, Java Moss only dies when it has extremely unfavorable growth conditions — it’s usually one of two causes: a drastic change in available light (i.e. complete darkness or close to it), or it’s grown too thick to allow light/water flow into the interior of the plant.
You can solve both by doing a few things:
1: Ensuring enough light is being provided, and that the light is suitable for growing plants. That means it outputs PAR, not just light for humans like lumens or lux. You might also consider increasing the photoperiod slightly and increasing the strength of your light source.
2: Ensuring that water flow is strong enough around and through the java moss. Flow is the main distribution method of nutrients around your tank, and since plants can’t move to where the nutrients are the flow has to be enough to bring the nutrients to them.