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Re: Mini-algae palm trees

Jorge asked:
"A couple of weeks ago I noticed these small algae? plants on the side
of my tank. They are very small, less than half a centimeter. They
are attached to the glass and the other end has 5 or 6 thinner arms
or branches that have an appearance an umbrella frame. Can anyone
tell me what they are?..."

Sounds like a Hydra to me. They aren't algae, and they aren't plants - they
belong in the same phylum of animals as corals, sea anemones and jellyfish.
Members of the Class Hydrozoa are commonly found in freshwater habitats all
over the world, and yours probably came in attached to some plants. I don't
know where you live, but there is supposedly one European species which
harbours symbiotic green algae within its tissues, which gives them a green
color. Other species, sans the algae, can be grey or brown - but they are so
tiny it can be difficult to assign any specific colour to them.

They are generally harmless to anything bigger than a baby brine shrimp or
the newly hatched fry of some egg layers (like for example, Dwarf Neon
Rainbows) - this is primarily because they are so small. The Hydra catch
their prey with those little tentacles you can see waving from one end of
the animal (the other end is attached to a solid substrate). They sting
their prey and then swallow them whole - so they can only catch and kill
very small prey.

I doubt that they are responsible for the deaths of your Ottos - they are
much too small to hurt an adult fish. Unless your tank is totally infested
with them, I wouldn't worry about them - its likely that the fish in your
tank will eat them before any population explosion turns them into a

Just don't go "ewwwww" and get all upset over them...unless you are trying
to breed egglayers in the same tank.

James Purchase