Soft hornwort, Ceratophyllum submersum, is far less well-known and less frequently cultivated as Ceratophyllum demersum. Like the latter, it is distributed almost world-wide and grows mainly in stagnant waters rich in nutrients, some of which periodically fall dry. Considering its natural habitats in Central Europe we might safely say that it prefers overall warmer locations than C. demersum.
The leaves of C. submersum fork three- to fourfold and end in 6 to 8 threadlike tips. In comparison, the leaves of C. demersum fork only once or twice, ending in 3 to 4 tips.
The leaves of C. submersum are generally finer, softer and more bendable than those of C. demersum, which are thicker, more brittle and often carry clearly distinguishable spikes.
Whereas the stem of C. demersum can be of a more or less reddish brown colour, the stems of C. submersum are always light green. The light green leaves of C. submersum, however, may assume an orange brown tint under very strong light.
Coon's tail is an undemanding rapid grower just like C. demersum. It does well under moderate light, however, under strong light it may attain a reddish tint. As it is a rootless plant, it can be left floating just under the water surface, or its stem ends may be stuck into the ground. It does not require the addition of CO2, however, a carbon dioxide injection accelerates its growth, as does a high macronutrient concentration in the water. Due to its rapid growth rate it has to be trimmed often, or is recommendable for larger tanks. Its stems ramify relatively well.
C. submersum can be an interesting alternative to C. demersum as its foliage is finder, and as it looks more delicate than the latter. It can be used just as well as C. demersum as a free-floating plant providing cover for fish fry in raising tanks.
|Light||medium to high|
|Temperature tolerance||4 to 30 °C|
|Optimum temperature||15 to 30 °C|
|Carbonate hardness||5 to 21 °dKH|
|pH value||6 to 8|
|Carbon dioxide (CO2)||5 to 40 mg/l|
|Nitrate (NO3-)||10 to 50 mg/l|
|Phosphate (PO43-)||0.1 to 3 mg/l|
|Potassium (K+)||5 to 30 mg/l|
|Iron (Fe)||0.01 to 0.5 mg/l|
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