Since the below listed links provide a great deal of information, I will just touch on what I believe are a few key factors in keeping most marine fish species.

   Feeding :  It is still very common to be told that any of our fish should be fed a single meal each day with enough food put into the tank that the fish can consume within a few minutes. I believe this is yet another carry over from the keeping of freshwater fish, strange as it may sound, but marine fish and freshwater fish are very different in almost every aspect other than the basic fish shape. One very important difference is that marine fish move food through their digestive tracts much faster. This is due to the fact that marine fish spend their entire day picking away at extremely small food items, mostly zooplankton that drifts by in the currents, while some species will also pick off small food prey from the substrates as well. Regardless of wether the food is stationary or drifting by, it is all very small amounts. As such, their digestive systems have evolved to match how much the fish normaly consumes at one time, and being very small amounts, it allows the digestive system to move the food through much faster than their freshwater counterparts. So when we feed the fish one large meal, the majority of that food ends up shooting right out their butts as partialy digested food, meaning that a good deal of that food is not only wasted, since the fish gained nothing from it, but it also adds a significant source of nutrients to fuel algae growth and degrade our waters quality. Since the fish only recieved that one meal, and could only gain a fraction of the nutrition out of it, they are in effect, slowly starving.  Knowing this, I feed my fish very small amounts at one time, and at frequent intervals throughout the day (at least three times) to ensure I am providing their digestive systems with a better suited feeding regime.

   Fish Size :  How many of us have bought a tang or large angelfish species as juveniles and put them into our 40 or 50 gallon aquarium? I know I have, and it was not long before I wished I had not. I of course told myself just as many of you did, that I will get a larger aquarium before the fish gets too large for the aquarium it is in now. Yeah, like that ever happened. Which means I ended up having to either trade the fish in, (always at a loss also) or give it away to someone who had the proper environment for it. While stressing out the fish the entire time. Thankfully, for me, I learned that lesson a long time ago and do not find it hard now to restrain myself from impulse "gotta have that!" purchases or captures. Although I could get away with it now since its only a matter of driving down to the ocean and releasing the fish, I would still rather not have to tear my aquarium's landscape apart just to catch one fish. But the one only real good reason to not do this, is that it simply is not fair to the fish. Yes, I know, they are just "fish", but once we designate something as a pet and not a food item, that designation brings responsibility with it, or at least it should.

   Since it seems that a good many of us do not fully understand the actual differences between saltwater and freshwater fish, and why saltwater fish need to be acclimated to our aquarium's salinity,  yet can go right into either hyposaline (lowered salinity) or a freshwater dip, the below should clarify that there is indeed a great difference between the freshwater and saltwater world.

Saltwater fish

• These fish are hypotonic to their surroundings. This means their blood has a higher water concentration than the surrounding sea water.
• As sea water passes through the mouth and over the gill membranes, water molecules diffuse out of the blood into the sea water by osmosis.
• These fish must replace the water which they constantly lose by osmosis
• They can also only afford to produce a very small volume of urine.
• Drinking sea water brings a large quantity of salt into the blood and this has to be removed.

• To replace the water they lose, saltwater fish drink sea water.
• To produce a small a volume of urine they must have a low rate of filtration of water into the kidney tubules.
• This is done by having a kidney with relatively few small glomeruli.
• Salt is removed by chloride secretory cells in the gills, which actively transport salts from the blood into the surrounding water.

Freshwater fish

• These fish are hypertonic to their surroundings. This means their blood has a lower water concentration than the surrounding fresh water.
• As fresh water passes through the mouth and over the gill membranes, water molecules diffuse from the fresh water into the blood by osmosis.
• These fish must produce a very large volume of urine to balance this large intake of water.
• This large volume of urine carries salt with it, and the salt has to be replaced.

• To produce a large volume of urine the fish must remove a large volume of water from the blood by having a high rate of filtration into the kidney tubules.
• This is done by having a kidney with many large glomeruli - capillary networks from which fluid is filtered at the start of the kidney tubules.
• Salt replacement is solved by chloride secretory cells in the gills, which actively transport salts from the surrounding water into the blood.

THE NUTRITIONAL VALUE OF LIVE FOODS  -  PART TWO  -  What better way to increase the health of your fish than by providing it will some very nutritional diets.

THE USE OF QUARANTINE TANKS  -  This should be one of your first purchases and used for everything.

FISH CARE GUIDES  -  Basic care information of some of the more popular fish families kept.

FISH PROFILES  -  Detalied care and feeding information on a great number of fish families.

WHAT FISH EAT  -  A good article explaining the dietary needs of fish.

HOW TO CATCH / REMOVE A FISH  -  There will come a time when you will have to do this.

Still not sure of what a specific species needs ? Ask Dr. Frank Marini within his forum which is dedicated to the care and husbandry of marine fish.