Marimo Moss balls (Algae!)

Marimo Moss balls (Algae!)

Marimo Moss Balls are made from an algae called Aegagropila brownii. It used to be classified as A. linnaei, but that species was synonimized into A. brownii a while back. Aegagropila is in the Pithophoraceae family, of the order Cladophorales. A. brownii is extremely slow-growing. We're talking an inch a year in ideal conditions. It's *not* a nuisance algae.

It grows in 3 forms in nature.
1) It grows attached to hard surfaces in short, thick tufts and carpets.
2) if there are no hard surfaces for it to attach to (usually lakes with fine silty or muddy bottoms), it grows in loose mats/webs along the substrate.
3) in very specific circumstances, the water currents will roll those loose webs/mats into balls. In Japan, these balls are called Marimo and are sacred to the Ainu people. They also occur in some glacial lakes in Scotland and northern Europe. They are protected in most areas where they form. Real ones are quite light and fragile, often with a hollow center.

Since they're rare and often protected, most of the ones in the hobby are man-made. The second growth form is harvested and rolled into balls by hand or machine. The resulting balls are much more dense and durable.

The problem is that, like many actual mosses, it has a tendency to pick up epiphytic hitchhikers along the way (note that this is an accurate use of the term "epiphyte", where a plant is growing non-parasitically on another plant. Algaes are the only true epiphytes that I know of in the hobby).

Lots of people get algal infestations in their tanks. Algaes that like to hitchhike on mosses and similar plants tend to be Cladophorales Algaes of the more troublesome genera, like Cladophora, Rhizoclonium, and Pithophora, which look superficially identical to Aegagropila. These pesty algaes thrive on accumulated mulm. Mosses and similar plants that accumulate mulm in them are prime targets and A. brownii balls are no exceptio

So whenever someone has such an infestation and has owned A. brownii balls within the last year or so, the balls get blamed for it. It's possible that a pest algae hitchhiked in on them, but it's also possible that it was introduced through any of a number of other vectors, and frankly, most people haven't the foggiest clue what algae they have. If someone looks at a picture of a green filamentous algae and rattles of a "that's Clado" or anything like that, you can safely ignore that. You need microscopy to identify a genus in 99% of all cases. There are a few exceptions, but even then you need a damn good closeup or extra information.

There are stories of A. brownii balls being other species, but I've never seen such claims substantiated. Agaegropila is a rare case where we can make a pretty good assumption of the ID based on a few details, the most important detail being its rate of growth. It is an incredibly slow growing algae. It actually grows fastest in cooler water, which is rare for a freshwater algae, but this is still just *so* slow.