NANFA-- Golden Shiner Question

John B (
Thu, 18 Sep 2003 22:13:51 -0500

My 55 gal is quickly becoming quite a biotope tank! I've got very nice
stands of Chara and Nitella collected from nearby waterways in addition
to Vals, Ludwigia etc. This tank was recently reestablished with 1 -2"
of potting soil beneath the gravel (1"). I had a break out of a stringy
but branched algae. When I ignored it for a few days it would bunch up
and look like green cotton balls on the substrate, just like in the
creeks and ponds in late summer nearby! I put in a couple of weed
shiners and a golden shiner and Wham, its gone. I watched as the fish
tore into the stuff like it was a Ceasars' salad! It is mostly gone
now. The weed shiners always looked fully fed even though I went for
days without feeding them. So they were certainly sustaining themselves
on the algae. Same with the Golden.

What capabilities do these fish really have in digesting the algae? The
Golden has apparently take to the Nitella because I observed nearly two
inch long strings of the nitella streaming from its vent. Nitella is an
algae, but a higher algae. The Golden seems to be only partially able to
digest Nitella. Previously the Golden's feces looked very green like
the algae (just bundled differently!)

What mechanisms do the fish have to break down cellulose? Is there a
significant amount of microflora and given a sustained diet of plants
would one expect more efficient digestion?I know how a cow does it but I
can't imagine that the systems are the same given the different

Well, I found the answer to my own question:

>An herbivore strategy: fermentation
>Herbivores counter the low digestibility of algae and plant materials
by increasing gut residence time (=reduce gut passage rate[or longer
gut]), but this has obvious limits: if passage rate >falls to zero,
nothing is being digested
>They also consume a lot more food: herbivores eat about 3X more than
>They tend to reduce energy and nutrient requirements; one won't find
herbivores among high-performance swimmers
>Finally, they can harbor anaerobes to ferment
>herbivorous fish have an elaborate gut flora, including largest
bacteria known
>these anaerobic bacteria break down cellulose, and produce fatty acids
as an energy source, exuded and absorbed by gut, along with extra
bacteria which are digested

Anybody have anything to add? I would guess that the shiners, given
largely a plant diet would eventually waste away?

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