Growing Plankton in Biotope Tanks

Biotopers might like to try an ‘open ocean’ experiment to improve the water quality of their system and provide extra fish-food.

‘The Open Ocean’ suggests trying to grow plankton – here are a few further thoughts.

Choice of Zooplankton

Many copepod species could arrive accidentally with ‘live rock’, or they might be obtained from a fellow aquarist, but if you begin like this you will have no idea which species you are rearing (this might be fine for feeding the fish, but it will limit the scientific value of your observations). If you want to increase this scientific value then you will need to know which species you have. I would suggest trying a harpacticoid copepod, because they can graze phytoplankton or eat detritus, are very robust and many small fish like to eat them. You might have to splash out and buy a pure culture (maybe of Nitokra lacustris).

Choice of Phytoplankton

Again it is perfectly possible to ‘see what arrives’ in your tank, but as with the copepods (above) you will not know what you are feeding your copepods on and the scientific value will be limited. Once again you might decide to fork out for a pure culture (maybe of Thalassiosira weissflogii).

Light Intensity

N.lacustris has very small young which do not swim and will feed in the sediment at the bottom of the tank. When they grow into adults (life-cycle of 10/12 days) they will begin to swim weakly in the water and graze the T.weissflogii. The trick will be ensuring that their plant food grows at the correct rate, and experimenting with different light intensities and day-lengths could get you there!

If you try this then please report your findings by contributing to the discussion.