Matt,
The two measurements you want to work with is length plus width of the tank, open water only. If you try to use LxWxH, you end up comparing the length of the fish to the volume of the tank, and it won't work.
Here is my first attempt at a method for quantifying swimming room for fish. I sent it to Practical Fish Keeping in England, so it didn't get much exposure outside of Great Britain, but I noticed that they put it up on their web site a short while back:
http://www.practicalfishkeeping.co.uk/content.php?sid=3048
I've since revised the procedure, refined the numbers a bit, and the new version will be coming out next year in Aquarium Fish International, so it should get broader distribution then. Is this method perfect? Of course not, but it is better than just guessing. One caveat is that it only considers the swimming roon needs of a single fish, so multiple fish in a tank still need to be dealt with "off the cuff". I've applied it to fish from 1" long zebra danios to the whale sharks in the Ocean Voyager tank at the Atlanta Aquarium, and it seems to work pretty well.
Jay
Jay,
Thank you for your reply. It is extremely helpful, and great to see someone apply some degree of science to a topic which is mostly governed by conjecture and baseless opinion. I have long been an advocate of apply the rule of thumb that a tank should be 6-8 times the length of the expected captive adult size of the fish..... and at least twice as wide as that length..... and applying the same logic as you when determining which end of the 6-8 scale it should be i.e. sedentry / maneuverable / cruisers. And of course, as you have pointed out - rules of thumb are just that, and a degree of discretion needs to be applied..... for example not all tangs are eaqual.... such as a naso tang and a yellow tang. Please see my signature:
Rules are for the obedience of fools and the guidance of wise men."
"Nemo mortalium omnibus horis sapit" - no man is at all times wise.
Your forumula makes much more sense to me..... for example, a 4x4x2 square based tank is equal in volume to a 8x2x2..... but some people would say that you cannot keep a larger fish in the 4x4x2 because its not long enough..... a weighting factor needs to be applied...... and I think your formula works well.
One thing perhaps you could offer further guidance / explanation on is the "open water" aspect. For example, in my proposed tank of 54"x30"x30", a couple of scenarios could exist.
Scenario 1: I keep the aquascaping low and flat, so it is no higher than 12" into the water column, letting 18" above it..... does that mean I can apply:
52+30 = 80
sedentry: 80/(3.5-5) = 16-23 adjusted adult size
maneuverable: 80/(5-7) = 12-16 adjusted adult size
cruisers: 80/(6-8) = 10-14 adjusted adult size
Scenario 2: I design a very open aquascape, where fish can swim in, around, through, and under the rockwork - relatively unrestricted..... still allowing say 9" front and back of a long narrow central island bommie....
So I would say 52" + (9" + 9") = 70"
sedentry: 70/(3.5-5) = 14-20 adjusted adult size
maneuverable: 70/(5-7) = 10-14 adjusted adult size
cruisers: 70/(6-8) = 9-12 adjusted adult size
Scenario 3: Less effective aquascaping, essentially reducing the open width by 50%:
52+15 = 67 with corresponding sizes of-
sedentry: 13-19
maneuverable: 10-13
cruisers: 8-11
So if we are to be conservative about it (based on preferred minimums of 1:5 / 1:7 / 1:8) then the max (adjusted) adult sized fish should be:
sedentry: 13 (say a volitans @ 15"x0.66 = 9.9")
maneuverable: 10 (say an emporer angel @ 15.7"x0.66 = 10.4")
cruisers: 8 (say hippo tang @ 12.2"x0.66= 8")
My own personal rule of thumb, which has stood to me well over the years of 6-8 times the length would equate to:
54" / 6 = 9" for sedentry - maneuverable
54" / 8 = 7" for maneuverable - cruisers
This would be slightly more conservative than your formula, but the similarity is more than coincidence, in my opinion, ad it validates yours and mine formula..... as such (albeit yours more scientific and ocmplex :thumbsup
Where hte nay-sayers will jump on board here is they will contest that an emporer angel, will grow larger than 10.4" and is more of a cruiser than a "maneuverable" species...... to which it could be counter argued that if we use "scenario 2" above for aquascaping and put the fish into lower end of the cruiser at 1:6 (because it cannot be argued that an emporer is as much a cruiser as say a naso), then we get 12"..... and there are not many captive grown (from juv.) emporers more than 12" in captivity....... so it still holds water.
I think this is an extremely interesting discussion. I am generally very conservative in my stocking plans, and for the record would not personally keep an emporer in my proposed tank..... at least not an adult one..... but it certainly makes more sense to me than arbitrary and guestimated rules. It would be very interesting to make a drop-down-menu spread sheet in MS excel. Of course, discretion and sensibility needs to be applied..... particualrly as you noted, when interactions with tank mates is considered for example..... and certain fish species like passer angels for example need special treatment due to abnormally higher aggression etc.
I would be extremely interested to hear back from you, to see if I have interpreted your formula correctly.
Thanks for sharing!
