- Tidal Pools
by Paul_Wilford/mindlink.bc.ca (Paul Wilford) (7 Mar 94)
by Paul_Wilford/mindlink.bc.ca (Paul Wilford)
Date: 7 Mar 94
>>Steve Liu <drlovemd-at-jhunix.hcf.jhu.edu> wrote:
>>>I live in the orange county/los angeles area of southern california.
>>>are beaches here that have have tide pools with lots of neat inverts like
Here in Vancouver a cop I asked about collecting said that it was ok. I also
asked about taking cuttings from Stanley Park, and he breezed through the
regulations covering that. I suspect that what he meant was that he'd charge
someone for taking some evergreens for Christmas, but that he wasn't going to
go after someone picking up a starfish. I still don't know if there are
regulations covering collecting, since I think he was implying that an
officer's discretion precluded a charge.
I trust you know the basics of keeping a marine tank, are looking for a cheap
and interesting alternative to a traditional tank, and are willing and able
to give your collection the necessary care and resources. Judging by your ID
(drlovemd), I'm sure that is so.
I have what passes for a tidal pool tank. I write 'passes' because I think a
tidal pool tank stops being representative of a tidal pool very quickly as
the population adjusts to the un-natural environment.
The inhabitants come from different part of the shoreline, the temperature is
wrong, the lighting is wrong, the currents are wrong, the water chemistry is
all wrong, there is no tidal flushing, and the animals can't leave. About all
my tank has in common with a tidal pool are walls and memories.
It's true that animals in tidal pools experience a range of temperatures and
salinity and may seem to be very hardy; but don't forget that the intertidal
zone is a extraordinarily complex environment.
Despite their apparent hardiness, intertidal species seem to exist in an
at-times very narrow niche in an extremely heterogenous environment. Just
take a look at all of the different strategies that the animals use to adapt
in the intertidal zone to get an idea of the diversity of avenues they have
to exploit and the consequent dependancies they have. I think this is a
uniquely complex microcosm, and you will have a hell of a time trying to
maintain an artificial environment that suits the lives of your selected
Perhaps my biggest mistake was in going along with conventional wisdom and
putting in a gravel bottom. Survival was poor and I replaced it with a
broken shell bottom, which seemed to be better. I graduated from being able
to keep crabs and fish to being able to support barnacles, chitons, and
mussels for months at a time (I increased the activated carbon filter size
at the same time). The shells came from the same general area as the tidal
pools, but were in a 'beachy' area.
The substrate is a problem because it isn't typical of a tidal pool, and can
support species which are not in tidal pools in significant numbers.
Nematodes took up residence in the substrate, and I now cannot keep a number
of animals that normally live in the rocky tidal pools - yesterday I put in a
bristle worm and within half an hour it was being killed by a swarm of
nematodes. The things just rise en mass out of the gravel and envelop the
poor prey. It's kind of creepy. If anyone know what eats nematodes, let me
In addition to the (non-organic) environmental factors, I think that there
are fragile associations of specific animals which we have to consider before
stocking a tank. You will have to be very careful about introducing a
species which will destroy whatever balance you have achieved and which may
prevent your being able to support desired species.
Most of the fun of a tidal pool tank is in discovery about new species that
you have collected and introduced. A few poor choices and your options will
be sharply limited from then on. I found that the easiest animals to keep are
crabs (after 'todes). Unfortunately, crabs can be very destructive and will
intimidate other animals. Despite their outstanding ability to keep the place
spotless, I returned the crabs several months ago. Now my anemone eats
again. It's why the bristle worm broke all records by living a whole half
hour before the nematodes got him.
And don't overstock your new tank just because animals are plentiful. At
times I've put in too many barnacles and mussels only to have a massive
die-off overnight. There's nothing like plunging your arms into a murky,
fetid, and foaming aquarium of rotting molluscs. I stood beside a 3-day dead
whale a few years ago and thought it smelled tame in comparison.
Geez, that was fun. I should have stayed in biology. Anybody else got tidal