- A few years ago, ultra low nutrient systems
were all the rage.
Chasing fluorescent colors in their acropora,
reef keepers following that system
stripped every possible organic substance from their water
by feeding fish sparingly,
the copious use of vodka or bio pellets, bright lighting,
and strong protein skimming.
Without any nutrients in the water, the reasoning went,
algae couldn't grow and the symbiotic dinoflagellates
that live in our coral's tissue, but tend to be brownish,
well, they'd give way to the fluorescent proteins
that were otherwise blocked by those cells.
Hi, guys and girls, I'm ReefMan,
and today we are exploring exactly the nutrients
that feed wild reefs, where they come from
and the tendency of reef keepers
to only include larger reef fish
like tangs, angelfish, or anthias in their tanks.
Smaller reef fish wildly outnumber the larger species
on wild coral reefs, and when I say small,
I mean absolutely tiny reef fish, that often grow no longer
than your pinky finger.
These fish provide a huge percentage of the eggs, larva,
and fish that feed wild reefs.
An ultra low nutrient system is easy to recognize
when you see it, although they're less common now.
They're characterized by clean glass, little or no algae,
and bright, but somehow unnaturally unsaturated colors
in the coral.
It's an aesthetic that a lot of people strived for
in the past, but thankfully we've moved on from it
as the best practice for keeping coral in our reef tanks.
Now, of course, it is true,
if you measure the water chemistry
from a pristine wild reef, you'll find very little
of the chemicals that we reef keepers care most about,
but if you look at everything in the water,
even the particulates, over time,
you'll find all sorts of eggs and larva
of all different sizes.
Of course, we can't yet feed that sort of thing
in our tanks, so all of that is lacking
in our home aquariums.
In fact, it's not just the eggs and larvae that are lacking.
A lot of us, myself included, have overlooked the tiny fish
that make up those reef ecosystems in our larger aquariums.
We concentrate on fish that are out more.
They're more flashy, more colorful,
things like tangs and angelfish, but on wild reefs,
gobies far outnumber tangs.
Should our home reefs reflect that perhaps?
It would be interesting experiment to try.
Those fish seem to be common in nano reefs, I will admit,
but as tanks get larger and larger,
they're less and less common.
Now, on this channel, if you've watched my videos,
you know that I've stressed over and over how beneficial
it is to feed our corals, just like we feed our fish,
but where does that food come from in the wild?
Well, it turns out that, in part,
it comes from those tiny reef fish that populate the nooks
and crannies on wild reefs.
Fish like gobies or blennies live their entire lives
extremely fast on coral reefs.
In fact, we've recorded up to 70% mortality
for week to week.
Now, if 70% of a population is eaten or dies every week,
there's gotta be a huge amount of eggs and larvae
going back into the water to sustain that population,
and it turns out there is.
Gobies and all the species in that set of fish alone
contribute almost 40% of the larva
that are found in the waters of coral reefs.
Add in the blennies and you're nearly to 50%,
and if you account for the rest
of what we call cryptobenthic reef fish,
then those fish account for about 65% of the larvae
in the water at any given time.
They have to reproduce in such quantities,
due to their extremely high mortality rate.
In the wild, gobies only live a few years if they're lucky.
The larvae of those cryptobenthic fish
also tend to be staying a lot closer to the reefs
that they're born on than that of larger reef fish,
like tangs, which spawn into the water column.
Damselfish larvae are the fourth most common,
but as you might know from your clownfish,
they attach eggs to a surface and then guard them.
With close to 700% yearly population turnover,
these cryptobenthic fish and their larvae
are a major source of food for pretty much everything
with a mouth.
Coral eats the eggs and larvae, fish eat the adults,
and of course, crabs and worms clean up
whatever's left over.
You won't see any of this on a chemistry test,
and so it'll probably be missing from your home aquarium
if you base it just entirely on the chemistry,
like those ultra low nutrient systems did.
This isn't to say that we should ignore chemistry.
Obviously, water quality and the chemistry
is a critical component of a successful reef tank,
but we also shouldn't ignore the food requirements
of our coral.
Interestingly, because their larvae do stay so close
to the reefs on which they're born,
and with such a high rate of turnover,
the gobies and blennies have created just a huge number
of species, some of which are found only
on a small number of geographically close reefs.
We know of over 2,000 species of gobies
and about 900 species of blennies.
Compare that to larger fish, like tangs,
which spawn in the water column,
where the currents distribute their larvae widely,
we know of only 86 species of tang.
Of course, as usual, there is a paper that sparked this line
of thought for me as I read it.
Also as usual, it's linked down below in the description.
You should check it out.
It's open access.
It's titled "Demographic Dynamics
"of the Smallest Marine Vertebrates
"Fuel Coral Reef Ecosystem Functioning".
Check it out, I mentioned it is open access.
That means it's free for everyone to read.
So thanks for watching.
Stay safe, COVID's still out there.
Consider subscribing if you haven't already
and you enjoyed this video.
Have a fantastic day.
Bye.
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