Bio-Load Estimates

[weez1959]

Hi Lee,
I know this isn't my thread but I was wondering how you calculated these bio-loads. I've been wondering how to figure this out myself

[leebca]

It's your thread now. I moved the post into its own thread.

How many fish?

So often asked but not easily answered.

Decades ago it was shown how bio-load was, in essence, the criteria of fish capacity -- The bio-load carrying ability of the aquarium/system and the bio-load each fish puts on the system. But what average hobbyist could do the complex computations to get a reasonably reliable estimate? Could the average aquarist estimate body mass and would that be good enough? The inches-per-gallon scheme was used in by freshwater aquarists and it came over into the marine hobby. It was simple and really wrong at the same time!

Obviously marine fish length was not a means to determine what bio-load the fish puts/places on a system. Does the 4 inch long and thin Butterflyfish (e.g., Copperband) put the same bio-load on the aquarium as a 4 inch long and thick Harlequin Tusk? I think everyone sees the uselessness of using inches per gallon to determine how many fish-inches can be put into a marine aquarium. But there's nothing to really replace the inches-per-gallon scheme other than experienced aquarist's opinions and what appears to be subjectivity.

I knew that the mass, consumption (of food), wastes produced, etc. could be scientifically calculated. But this kind of calculation was not something the hobby could use. After all, the reason inches/gallon was being used was because it was simple. The most-used scheme would be the easy scheme.

We know too that it isn't the gallonage of an aquarium which determines the aquarium bio-load ability (capacity). The system configuration determines bio-load capacity. That is, the bio-filtration method, circulation, other filtration, substrate, skimmer, live rock, refugium, etc. So there had to be a similarly easy means of estimating the bio-load ability of the system.

Both the bio-load ability of the system and the assignment of bio-load to fishes (mostly) and nitrogen waste producing marine life, was something I worked out. I use that information. It's just not as simple as I wish it was, because there are so many different system configurations and types of fishes.

Then there is a somewhat intangible part to the scheme. This is the space a fish needs (either actual/real or from the fish's perspective). Some fishes swim a lot in the open ocean, others stay and guard specific areas. A mated pair of fish will want and need certain space that doesn't really relate to their true bio-load. Same with fishes like the Tangs. The sub-adults of these fish join large schools that travel for up to 25 miles per day. In captivity, extra space and distance in the aquarium is needed. So in the scheme I devised, such fishes are given 'normal' bio-load numbers, but are in a category of fishes that require a minimum of X type/size aquariums. Thus the bio-load unit scheme comes with a set of rules. Not so simple!

[weez1959]

yikes!!

[weez1959]

Ok, to give ma an idea,
My tank is 75g ('til the spring, working on 125-150, woo hoo!) with a 25g sump, a remora pro skimmer, about 100lb live rock, and 80lb crushed coral.
My present fish are:

6 blue green chomis
2 false percula clowns
1 pyjama cardinal
1 strawberry dottyback
1 pacific sailfin tang

How would you say I'm stocked, bio-load wise?
Too much or room for more...

[leebca]

The live rock target should be about 2 pounds per display tank gallon. If you could nudge the live rock up closer to that mark, and guarantee circulation to exceed 100 gallons per hour turn over, then. . .

The system has a bio-load capacity of approximately 20 bio units.

Your current bio-load on the system is approximately 20 bio units.

The system is at its comfortable limit. Although the Sailfin will need moving to a larger aquarium once it reaches more than 4 inches in length (measured from tip of nose to caudal peduncle).

The way the system is now, it should be fairly easy to maintain good to excellent water quality and stress on the fishes is minimal.

[Fishyz]

How many bio units does a sailfin tang count for? How many for a yellow and convict tang? Thanks

[leebca]

A sub-adult Sailfin Tang will count for 3-4 bio units; the sub-adult Yellow is 3; the sub-adult Convict is 4. However the tangs have a 'rule' of requiring more swimming space.

[Fishyz]

I'm setting up a 90gal with a 30 gal sump with about 80-90 lbs of live rock. How many bio units would you say my tank could have? And would you recommend putting a small sailfin in a 90 gal, or should I consider a smaller tang instead? Thanks

[leebca]

If you would consider upping the live rock to about 175+ pounds, and guarantee a circulation of no less than 1200 gallons per hour the tank could handle up to about 24 bio-load units.

The Sailfin Tang is one of the smallest tangs suitable for the 90 gallon tank. No smaller tangs around. These tangs, if acquired when under 3" in length, will be okay in the 90. They will need a larger tank when they reach about 4" in length.

[Fishyz]

What would you say are some other suitable tangs for a 90 gallon? Many people have told me that a 90gal would be to small for a sailfin, but after seeing multiple people with sailfins in their 90's, i though maybe I could get one. The tang would be the only "large" fish in the tank.

[leebca]

The Genus Zebrasoma have a few of the 'thin' Tangs that grow slowly and not too large. The Yellow, Pacific Sailfin, Brown Sailfin, and Yellow-Tail Sailfin, are in this group. One in a 90 would be okay, as I mentioned, until it got to be over 4" in length. About the only one in this Genus not suitable for the 90 is the Indian Ocean Sailfin, a.k.a. Desjardini, Z. desjardini.