Tank size for Tangs? An evaluation...

[Diomedes]

What is natural?

Recently here at Canreef we had a heated debate over the maintenance of two small (3 to 5cm?) Paracanthurus hepatus (Blue tangs) in a 33 gallon tank with a 40 gallon footprint. I unfortunately added some slander and rude comments in an outburst of temper. I decided to make up for it by writing this post. I apologize to those who were offended, and I hope to have the opportunity to offend you again in the future, if only to have the opportunity to apologize again. HeHe Just Kiddin…

In the beginning of Scott Michaels’ book Marine Fishes he states that his “Minimum Aquarium Size” evaluation is the
“minimum suitable aquarium volume for an adult individual of the species. Of course, juveniles and adolescents can be housed in smaller tanks. Activity levels and behavior patterns of a particular species have been accounted for whenever possible…please note that providing as much room as possible will allow any fish to acclimate better…”

Now I understand that this is a MINIMUM aquarium size, but if SM is giving a 12.2” blue tang 100 gallons of space (some of which is filled with rock and sand maybe?) then I don’t understand how putting a 1.5 inch tang in a 40 gallon could cause so much emotion. This is because 12.2 inches in 100 gallons is roughly equivalent to 8.2 gallons of water per inch of Tang. My friend Sumpfinfishe is giving approx. 27 gallons of water per inch of Tang. This is much more space per inch of fish, and that isn’t even taking into account the width of such a huge 12.2” beast. In fact if SM were to give his 12.2” tang as much space as Sumpfinfishe, then he would have written the Min Aquarium size as 330 gallons. So it appears that Sumpfinfishe is giving his tang(s) over 3 times the minimum aquarium size recommended by a world expert. But hey, this is all just the examination of Expert advice. I have a heap of respect for Scott Michaels. He has studied marine biology (as I am doing now – 4th year), and can take some very very pretty pictures. But how did he come to his values for Min Aq size? I don’t know…All I know is that he puts a 7.5” tibicen angel in a 20 gal, a 45” (~4.9ft!!) moray in a 30 gal, a 2ft Coris Wrasse in a 135gal, a 20” Niger trigger in a 75, etc etc etc and the list goes on…Troy has recently expressed regrets over Scott Michaels Minimum Aquarium sizes, and upon closer inspection this would seem to be pretty darn accurate. But SM still has my devotion…his Reef Fishes Vol One is a beautiful book that shows the true depth of his knowledge. I also examined the Dr Burgess Atlas of Marine Aquarium Fishes and I found similar (and sometimes worse IMO) ratings for tank size versus adult length. So where does this all lead? Do I have the magic number of gallons per inch of tang? No, because if I did I would be up in Anchorage Alaska eating dinner with Dr. Shimek. We all have to trust our judgement and kill fish in order to learn. (~JK)

But this does go back to an important question for me…What is natural for a marine fish? In light of recent debates on this board and others, it seems to me that the question of what is natural for our fish (tank size, flow, feeding, water quality etc.) is always going to be a hot topic.
What is natural for your marine fish? Let’s first look at the factors that affect natural behaviors of fish in the wild:

1)Search for food (foraging, grazing, hunting etc.)

2)Competition with same species (intraspecific) and with others (interspecific)

3)Predation (actions taken to deter something from eating oneself – schooling, hiding etc.)

4)Reproductive needs (courtship, nesting, harems, schooling etc.)

5)Disease/Parasites (cleaning stations etc.)

6)Seasonal/Climatic environmental changes (tides, storms etc.)

Now how many of these factors influence a fish once it is in your aquarium?

1)They don’t have to search for food – in fact they probably are trying to get away from it half the time (HeHe)

2)They do compete with each other, but because of the enclosed space the competition is abrupt and usually one fish achieves dominance very quickly…after all there are only so many niches in your aquarium…mysis, brinnies, etc.

3)Once the fear of being eaten wears off (this takes a while in some cases) this behavioural stimulus is no longer present…until the hobbyist buys that cute little grouper.

4)Reproductive needs cannot be met (for most species) in most hobbyists’ aquariums. Does the drive to reproduce still effect behaviors? Sure. How? Don’t know, aren’t even close to understanding.

5)Yes Diseases and parasites shape behaviors in our aquaria. The fish tries to get away, can’t, then either dies or is cured.

6)Tides/Storms etc. don’t make an impact in most people’s tanks. Now power outages though….

So running down the list, there are very few things happening naturally in a typical saltwater aquarium. So what is “Natural” for fish in the wild may not be natural for fish in the aquarium. Look at Cats…is it natural for them to sleep 22 hours a day in the wild? What behaviors do they exhibit in the wild? How much territory do they roam, what food do they eat etc.? The point I am trying to make is that we have to be happy at the present time with as much space as we can afford to give our fish. I just use common sense to make up for my (and anyone else’s) lack of concrete knowledge on how much space a small tang needs…is he happy, eating, frolicking? I tend to worry about bringing out the life on my rock, maintaining properly unpredictable flows etc. But hey that’s my opinion, and I am sure many of you will disagree.