How to grow "HC Cuba"

Hemianthus callitrichoides (HC) 'Cuba' is one of the smallest ground creepers available in the hobby. It is popular as a carpet as its small size makes for a very fine carpet and contrasts well with even other small leaved plants. HC Cuba is notorious for being one of the harder carpeting plants to grow well in the planted aquarium. It is often called dwarf baby tears in the hobby, but this can easily lead to mix-ups as "baby tears" can refer to a couple of other plants as well.

A similar plant that is far easier to grow is Micranthemum Monte carlo, with the difference being insignificant at a distance especially in larger tanks. HC Cuba grows slightly faster than Monte carlo and has smaller leaves and stems. It is not as deep rooted as Monte carlo and requires more frequent trimming. HC Cuba plant requires a lot more CO2 to grow well compared to Monte carlo. Both plants will creep over rocks; but Monte carlo does this more aggressively.

Key Success factors

• Good CO2 levels - see guide here.
• Adequate lighting - 40umols at substrate +
• Good planting technique - plant separate small strands rather than bunches

Additional points:

• Lower temperature helps (< 26 degrees celsius)
• Possible to get good growth till 29 degrees or so. Exponentially harder above that. Tanks in the tropics with no chiller should avoid the hassle and just use Monte carlo.
• Fine, rich substrates help, but not a necessity (ADA powder)
• Not sensitive to KH; can tolerate higher ranges well (10+ dKH

Tissue culture HC can be sensitive to ammonia/raw new aquasoils. Especially using ADA aquasoil, pre-cycle the tank for a couple of weeks before planting to avoid melt completely.

For detailed steps on how to cycle a tank, click here.

Trimming HC all the way down to the bone/substrate line once in a while to remove old growth maintains a healthy carpet long term. Frequent trimming is necessary to prevent the carpet from being coming too thick, and detaching from the substrate as the bottom layer deteriorates.

HC Cuba plant grows quite fast when grown well; 1 tissue culture cup of plants will carpet a 1ft square area fully in less than 3 months.

Here, dwarf baby tears contrasts well with Bucephalandra Brownie Ghost.

without CO2?

A common question we get asked is, can you grow HC Cuba plant without CO2? Growing HC Cuba plant without CO2 has a failure rate of 95%. However, the remaining 5% will loudly advertise their success on Bragbook and social media; classic case of survivor-ship bias. Case in point, HC cuba grows without CO2 using strong lighting and soil in the tank below.

CO2 is paramount to HC's success, it is a relatively undemanding plant otherwise. It is one of the plants which is sensitive enough to CO2 levels that it is useful to grow small patches of it in every tank as living CO2 indicators. It gets thinner with more spindly upward growth in low CO2 levels.

Classic CO2 deficiency in HC - thin stems, small new leaves, upward reaching stems rather than creeping.