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/Go Rin No Sho of Business

Selling Compatible Marine Species

Bob Fenner  

All indications point to increases in emphasis in sales of and profits from marine live-stock, dry goods and systems. Successful retailers are aware of the habits and compatibility of the few to several hundred species of marine fishes, invertebrates and algaes available seasonally, and practice care in their selection and mixing. This article presents an introduction and some notes concerning the compatibility of marine species.

For the less-initiated: tropical marine organisms and habitats can be contrasted with tropical freshwater as being much more vivacious; "things" happen more quickly and overtly. The salt-water organisms in our care and sale are more active, aggressive and predaceous. Theirs is, in general, a much more "eat and be eaten" world than freshwater.

Most retail marine fishes and invertebrates are opportunistic omnivores: that is; given the chance, they will eat most anything. Though your references and the critter's structure and form may seem to dictate a strictly vegetarian, or at least restricted diet; be forewarned: If, when hungry (enough) and opportunity presents, most marines will gladly consume their tank-mates. What to do?

1) Learn: read as much as you can that's accurate, meaningful and significant on the subject. Particularly useful are current industry and hobbyist publications. Listen: to your suppliers. They are there to help you be successful. Their success depends on you.

2) Pick your livestock carefully. Healthy, well-fed and well-adjusted specimens are more compatible with each other and captive conditions. Some species are better mixed or not by numbers, pairs, sexes or size; know what you're selling. (see PSM 1/89, Successfully Selling the Popular Marines, by, who else? me) 

3) Take care in introducing. Acclimate your stock properly, with a consistent quarantine or at least dip process (see Freshwater and Marine Aquarium Magazine, 8/89 Acclimating Fishes by myself and Steve Landino) Stabilized, disease-free specimens adapt more readily.

4) Under-crowd your systems. Keep "mean" and questionable species and individuals isolated or eliminate them from your stock. Provide habitat for hiding/escape. Move bullied or bully specimens.

5) Keep up water quality. Higher nitrates and other metabolites are known to elicit more aggressive behavior in crabs and some fishes.

6) Feed and check on your livestock often. If possible, avoid feeding live foods that resemble tankmates! A useful anecdote here may illustrate a few points. Once we raised a small clown triggerfish in with a mixed group of small damselfishes. All went well for month's; selling and adding damsels. Then one day, while feeding on live brine with it's fellows the now four-inch trigger exercised an over-zealous over-bite and bit off a damsel. Subsequently we were out damsels every day till we learned that the trigger had learned it's tankmates were swimming Snickers.

Some General Notes on Non-Vertebrates:

Invertebrates are for best kept by systems by themselves; avoiding the lower specific gravities and therapeutics of "fish" systems. Some progressive stores with reef systems may be exempted.

More specific generalizations by group: (See blue-highlighted links for more husbandry information)


Are difficult to maintain alone or with many actively mobile species. Keep them in reef systems without large fishes, crustaceans or mollusks, if you can.

Anemones and Corals: 

May compete with each other in tests of "digestive dominance", stinging and eating each other. If you can't deal with a known group of compatible individuals or species you're cautioned to isolate or space your stock such that they cannot "reach" each other.


For the most part are best displayed in invert. systems. Some cones are dangerous to humans and outright piscivorous, while other's easily become tasty, expensive tidbits. Octopi and their relatives are capable and desirous of scarfing up whatever strikes their fancy. Keep them well fed. There are some notable mollusk exceptions for "fish tanks". Check with your suppliers for these.


Most of the common shrimp are compatible with each other and most smaller fishes. Provide adequate hiding spaces for molt times and intra-specific bouts.

Crabs and Lobsters. Most often should not be trusted with more than one per isolated space. With few exceptions (e.g. the Emerald Green, Mithrax Crab for instance largely eats algae) they will eat everything including your fishes if given the chance; and they are always looking for it. Even hermit crabs will greedily consume each other if no other fare is forthcoming.


Or Spiny-Skinned Animals. Seastars, Brittlestars, urchins and their kin are mostly innocuous, good mixers; & apparently unpalatable. A word of caution regarding the holothuroideans, variously known as Sea Cucumbers, Sea Apples, etc. These organisms may be hazardous to your business and holding systems health! If incompatible with your set-up and/or their tankmates they may quickly "throw up their guts" and more or seemingly spontaneously disintegrate taking the whole tank with them. So be cautioned: Show and sell these from an isolated, individualized invert. system.


Some popular groups are notorious eating-machine predators. Groupers and Basses, Snappers, Squirrelfishes, Triggerfishes, Morays and other Eels, puffer-like fishes, Anglerfishes & oh yes, this list could go on.... Suffice a few more generalizations. Do not mix organisms with large differences in size; in particular, bite-size of mouth. Pay particular attention when first releasing new stock. Move "decorations" to upset existing territories and watch for predatory & agonistic behavior toward newcomers. Surgeonfishes and others are able to inflict terrible wounds upon fishes they dislike. It is advisable to leave at least some lighting on overnight after introducing new livestock.

With (1) buying good quality, suitable specimens & (2) adapting them to appropriate environments & (3) maintaining these environs optimally, compatibility problems are much reduced. The weak link & salvation beyond these considerations is close, constant observation of your livestock and systems. Be aware of what is going on in the system's in your store and move specimens as necessary.


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