nano bioload equation

[Mihai]

Hi there,

I'm planning on a nano and I read most of the posts on the nano forum
and it seems that for nanos stocking is one of the most FAQs. And I
was thinking if we can come up with an approximative formula to
clarify stocking in a nano...

Something along these lines:

You can keep a nano in good health as long as you do 20% water
changes (with freshly prepared water) every week and your bioload does
not exceed your tank capacity.

Now to define bioload: for every inhabitant assign a tank capacity (in
gallons) that the respective inhabitant is messing up. I'm proposing
a few numbers here, just to give you an idea of how this works:


False Percula : 5
Clown Goby : 3
Firefish : 3
Zoanthid : 0.001/polyp
Mushroom : 0.005
Sun Coral : 0.2/polyp
Montipora Digitata: 0.001/cm
Mantis shrimp : 1
Turbo Snail : 0.1
Astrea Snail : 0.03
RedLegged crab : 0.05
BTA : 0.7
Clam : 0.5


If you're at half the bioload that your tank can sustain you probably
can go with 10% weekly water changes. If you're at double, you
probably have to go 20% water changes twice a week.

Notice that I'm not talking here about how much volume a fish needs
to feel well, but rather how much water it messes up. Hence a yellow
tang will probably be a 20 although it should not be housed in any
tank smaller than a 50 or 70.

I'm very new at the hobby and have 0 experience with the nanos, so I
can't make this list, but if one of you guys would put in the time and
effort to make such a list it would help a lot of people with stocking
questions.

I realize that the dynamics in a nano tank cannot be exactly captured
by a dry mathematical equation, however, I'm suggesting this as a way
to figure out an approximate ballpark, useful especially for
beginners. Of course, you'll get feedback from the tank itself that
will help you adjust your "calculation": if the algae get out of
control, your corals don't thrive, or (gasp) your pets die, your tank
is out of capacity although you may be "mathematically" OK.

If any of you guys with experience wants to take on such an endeavor,
I think that we should make this list as public as possible, perhaps
even publish it in a hobby's magazine (FAMA?).

In this case, we'll probably need some sort of validation for the
list. I suggest to look message boards on RDO, RC and nanoforums and
see good tanks and tanks with problems, compute the bioload capacity
for both and, hopefully, the tanks without problems have a bioload
smaller than the proposed limit and the other way around...

Any thoughts? Anybody's game for this? I'm willing to help with
anything I can (including suggestions and a validation of the list).

There is one more interesting data point: if one has a very low
bioload (say 1% of the nominal bioload), it should be able to go
without water changes for a very long time, say for two years (100
weeks). This is what I saw a couple of years ago at a "nature store":
they were selling sealed containers of about 1 gallon that contained
nothing except 2-3 tiny shrimps that lived off the algae growing in
the container and they were claimed to live for about two-three
years...

Theoretically the formula should hold for a big tank as well, but
there things are more complicated, because there are skimmers, algae
scrubbers, and other means to clean the water that make a significant
difference. Nanos are much simpler (we assume a nano without algae
scrubbing and skimmer).


Regards,
Mihai

 

[brandon4291]

neat concept! I think it will take a thread of good length to work out some predictions in these areas, as many hidden variables can arise and throw off the predictability but not if they are accounted for! You picked a fine place to start, we have lots of mathmatically-inclined individuals reefing around in here...

Such as, it's possible that nanos with sandbeds versus nanos with thoroughly-cleaned or no sandbeds would have different waste tolerances for a given bioload and feeding regimen. Other things like sun corals, for example, aren't really a high-bioload colonial creature in terms of nitrogenous waste excretion but they may count with a heavier rating due to the spot-feeding associated with them--and the general dispersal of this feed/protein into the system. I always look at feeding requirements as a critical factor in bioloading prediction. Size of the organism helps, but a vegetarian would be much more acceptable in terms of nitrogenous waste when compared to a preferential carnivore. I dunno, could we say that gobies for a given inch-scale would be less bioload than a hunter of the same size? Just a thought, let the brainstorms begin

 

[Anonymous]

I assume you're talking about a measure of something like total net waste excreted, maybe measured by something like moles of ammonia excreted per day or something.

Great idea but I think it's going to be very difficult to quantify this stuff because of all the outside variables, especially feeding as Brandon points out. Do you feed your BTA a lot, or a little? Do you feed your clam some phytoplankton, or none at all? (This one could potentially change the number from positive to negative) Do you strain out the juices when you feed frozen mysis? Do you have lots of natural algae growth to feed your blenny, or do you have to supplement it with natural foods? And 1000 other questions like this.

In any case, I believe small frequent water changes are important regardless of tank size or bioload in order to keep trace elements in levels as close to natural as possible.

But for a gross generalization, I'd say the average 10 gallon tank can handle two 3 inch fish of 'medium' build, say Ocellaris clowns or royal grammas.

 

[Anonymous]

Thats a neat little concept...The differential equation that would be needed to even form an idea of this would be enormous and complicated due to the different and numerous variables involved..If you invest in a neat little math program like Derive or Mathcad perhaps you can formulate a mathematical model of this :wink: .. It comes down to essentially math and chemistry.. Even to start something like this up would probably take a giant room filled with various tanks and setups and parameters...

 

[Mihai]

Hmmm... I wasn't talking about a differential equation, but rather about a truly simple equation involving only addition. Of course you can write the differential equation that tracks waste as a function of time, but that's not needed. However, if you think that it helps I have Matlab and Maple (vast improvements over Mathcad), and I'm not afraid to use them .

Matt, I wasn't talking about measuring stuff: that would be very difficult, expensive (I think) and time consuming. I was trying to draw on the experience of you guys that have some gut feeling about those numbers. You "know" that an anemone that's being fed is "more" bioload that, say a patch of 10-polyp zoanthid. What I'm asking you is to quantify it based on your experience.

Regarding the variance in feeding habits I admit that it can make a difference; however, we can consider such things as "typical" conditions: I don't have a clam, but I understand that you *need* to feed it phyto to keep it alive. Similar with an anemone (if you don't I assume that most people would not feed it in a nano which becomes the "typical" case).

How about if I'll try to make a long list of critters that can live comfortably in a tank <12 gallons, suggest some numbers and you double check them?

M.

 

[Anonymous]

Matt, I wasn't talking about measuring stuff: that would be very difficult, expensive (I think) and time consuming. I was trying to draw on the experience of you guys that have some gut feeling about those numbers. You "know" that an anemone that's being fed is "more" bioload that, say a patch of 10-polyp zoanthid. What I'm asking you is to quantify it based on your experience.

Regarding the variance in feeding habits I admit that it can make a difference; however, we can consider such things as "typical" conditions: I don't have a clam, but I understand that you *need* to feed it phyto to keep it alive. Similar with an anemone (if you don't I assume that most people would not feed it in a nano which becomes the "typical" case).

How about if I'll try to make a long list of critters that can live comfortably in a tank <12 gallons, suggest some numbers and you double check them?

M.

Depends on who you ask, and the size of the clam.

But yeah, I could definitely give you my gut feeling for some of those numbers for fish. I do think that photosynthetic corals are pretty much either 0 or negative in most cases though. You can pretty much fill up a tank with coral without worrying too much about bioload.

Here are the fish from the "Nano reef fish" list, and the #s I'd approximate for what you're thinking. These are the smallest size tank I'd put a full grown one of these fish in. Please note these are only for the species on the list. Obviously I would not put one of the larger Pseudochromis in a 6 gallon tank...

Centropyge argi: 12-15
All other Centropyges: 20
Serranocirrhitus latus: 20
Plectranthias spp.: 5
Liopropoma spp.: 6
Serranus spp.: 5
Gramma loreto: 5
Gramma melacara: 8
Assessor spp.: 5
Amphiprion ocellaris and percula: 6
Pseudochromis spp.: 6
Paracheilinus spp.: 10
Pseudocheilinus spp.: 8-12
Halichoeres and Bodianus: 20
Wetmorella: 10
Hawks: 10, except for Oxycirrhites I'd say 20
Blennies: 12-15
Damsel/Chromis: 4-5
Firefish: 4-6
Jawfish: 6
Stonogobiops spp.: 4
Gobiodon spp. (except citrinus): 2-3
Gobiosoma spp.: 4-5

 

[Anonymous]

Even some of those Centropyges I wouldnt even attempt in a 20g 4-6in.. I dont think one would want to put a Flame angel with two Perculas in a 20? Obviously common sense plays a big factor but for a novice such as myself may not realize the extent of a heavy bioload or lack there of..Coming from FW where you can get away with perhaps cramming a few more fish vs a SW where 1-2 fish in a ten is pushing it depending on the size and load of the fish..I also figure a fish that moves less such as maybe a hawk or an angler would secrete less waste, lessing the bioload but i could be wrong, Im not a biologist or an Ichthyologist by any means, just a hobbyist learning

 

[Anonymous]

I guess I didn't say it, but those numbers are assuming that the fish would be the only fish in the system. I consider a 20 to be the absolute minimum for all of the Centropyge besides the argi complex..

 

[Mihai]

Thanks for the time Matt, I think that the list is already very useful: it gives the people an idea on what fish they can keep in what volume of water (vast improvement over the list without numbers).

Now about the invertebrates... maybe we can go with sweeping generalizations, like:

shrimps: 0.3
crabs : 0.1/cm
hermits : 0.01
stomatopodes: 1
sea star : 0.1
urchin : 0.5
and for the corals... 0?

M.

 

[brandon4291]

Good call Mihai for most of the corals, at least a smaller decimal expression than the other forms of bioload considered!

Yep that numerical list of the Nano reef fish was handy, I looked right through it to consider stocking options for my medium-sized nano as soon as the skimming issues are worked out and it becomes ready to restock with fish again.

I see, those with fish experience would just add up all the feeding/waste variables associated with a given genus/sp and assign a rating so others could take a glance and get a general stocking idea.

 

[Anonymous]

Thanks for the time Matt, I think that the list is already very useful: it gives the people an idea on what fish they can keep in what volume of water (vast improvement over the list without numbers).

Now about the invertebrates... maybe we can go with sweeping generalizations, like:

shrimps: 0.3
crabs : 0.1/cm
hermits : 0.01
stomatopodes: 1
sea star : 0.1
urchin : 0.5
and for the corals... 0?

M.

Gets a bit tricky with invertebrates. I remember reading in a few places that an octopus, ounce for ounce, puts out THREE TIMES as much waste as a fish of the same weight. Clearly there are differing metabolic efficiencies between the two.

I'd like to tell you I knew how much a shrimp or urchin puts out in comparison to a similar sized fish, but I don't. If you do some searching on the web there is probably some info out there like this.

But FWIW, I would not put ANY full grown sea star or urchin in a tank smaller than 20 gallons. I can't think of one that isn't a coral predator or needs a lot of live rock to graze on. Not to mention their tendency to knock over small frags we like to keep. I would rate the crustaceans a bit higher too. A full grown skunk cleaner is big, like 4" long...and some mantis shrimp get a foot long!

 

[Mihai]

Gets a bit tricky with invertebrates. I remember reading in a few places that an octopus, ounce for ounce, puts out THREE TIMES as much waste as a fish of the same weight. Clearly there are differing metabolic efficiencies between the two.

I think that because the octopi only live for an year or so they have to make up for it (leave at a higher rate). Probably that's why... or messy eaters?

I'd like to tell you I knew how much a shrimp or urchin puts out in comparison to a similar sized fish, but I don't. If you do some searching on the web there is probably some info out there like this.

I doubt... I don't even know where to begin... what gets consumed by those animals that needs replacement? I mean, why the water change? (I want an answer more specific than "metabolic waste")... maybe the guys in marine biology may know about that...

But FWIW, I would not put ANY full grown sea star or urchin in a tank smaller than 20 gallons. I can't think of one that isn't a coral predator or needs a lot of live rock to graze on. Not to mention their tendency to knock over small frags we like to keep.

I agree. Except maybe for a small Fromia sp.for sea star?

I would rate the crustaceans a bit higher too. A full grown skunk cleaner is big, like 4" long...and some mantis shrimp get a foot long!

OK, then maybe the numbers should be per inch of animal?

M.

 

[Anonymous]

Gets a bit tricky with invertebrates. I remember reading in a few places that an octopus, ounce for ounce, puts out THREE TIMES as much waste as a fish of the same weight. Clearly there are differing metabolic efficiencies between the two.

I think that because the octopi only live for an year or so they have to make up for it (leave at a higher rate). Probably that's why... or messy eaters? Probably a bit of both. They need a lot of oxygen in the water too.

I'd like to tell you I knew how much a shrimp or urchin puts out in comparison to a similar sized fish, but I don't. If you do some searching on the web there is probably some info out there like this.

I doubt... I don't even know where to begin... what gets consumed by those animals that needs replacement? I mean, why the water change? (I want an answer more specific than "metabolic waste")... maybe the guys in marine biology may know about that...

I don't know if I'm understanding your question correctly...but you may try searching with the terms "metabolism", "efficiency", "ammonia", "compared" and "fish", for instance.

But FWIW, I would not put ANY full grown sea star or urchin in a tank smaller than 20 gallons. I can't think of one that isn't a coral predator or needs a lot of live rock to graze on. Not to mention their tendency to knock over small frags we like to keep.

I agree. Except maybe for a small Fromia sp.for sea star? I suppose, I thought they got pretty big though...?

I would rate the crustaceans a bit higher too. A full grown skunk cleaner is big, like 4" long...and some mantis shrimp get a foot long!

OK, then maybe the numbers should be per inch of animal?

I wouldn't put a Lysmata shrimp in less than 3 or 4 gallons. Same with a porcelain crab.
M.

 

[Mihai]

I wouldn't put a Lysmata shrimp in less than 3 or 4 gallons. Same with a porcelain crab.
M.

Got you here. However, we're not talking about suitability: as I said before, you would not put a tang into a nano... but from a metabolic point of view it can probably survive in a 10 with 20% weekly water changes. The minimum comfortable tank size for a fish is a different list...

Mihai

 

[Anonymous]

Hmmm, a full grown tang would literally have to be crammed into a 10 gallon tank, but yeah, I've seen them crammed in flow through tanks the size of a shoe box at wholesalers.

Lysmata shrimps grow fast, put out a lot of waste, and are fairly active. You'd have to do a lot of water changes frequently to keep one in a tank smaller than 2 gallons IMO, but I thought we were considering what could be kept in a certain volume *with a normal maintenance routine, i.e. 20-30% monthly*.

 

[Mihai]

Hmmm, a full grown tang would literally have to be crammed into a 10 gallon tank, but yeah, I've seen them crammed in flow through tanks the size of a shoe box at wholesalers.

I agree that it's totally inappropriate to keep a tang in a 10gal,
because it's so active and it needs the space and algae to graze, but
from a waste production point of view it's probably not more wasteful
than two clowns...

Lysmata shrimps grow fast, put out a lot of waste, and are fairly active. You'd have to do a lot of water changes frequently to keep one in a tank smaller than 2 gallons IMO, but I thought we were considering what could be kept in a certain volume *with a normal maintenance routine, i.e. 20-30% monthly*.

Sure, in the initial post "normal" maintenance was defined as "10%
weekly water changes". I don't contest your shrimp evaluation: I have
no experience with Lysmata, I was just pointing out that the
evaluation has to be strictly from the point of view of the waste
production. Hence, a Goniopora will probably be a 0.5 although is
totally inappropriate to keep it in any aquarium (I'm not looking for an
argument, here, just an example).

M.

 

[Anonymous]

Gotcha...and I still think a 3 or so is about right for a full grown Lysmata sp.