Feeding your Fish
Feeding the fish is an area where many beginning and even advanced aquarists can run into trouble. Over-feeding your fish will almost always cause problems in your aquarium, so the easiest rule is to not overfeed. However, beyond just the amount of food that you feed your fish there is the important question of what type of food you should feed your fish. This article will cover many of the different food types available, and will give some suggestions to the amounts and types of food that you should feed to different types of fish.
FOOD TYPES
The most common food that you'll find is flake food. Pet stores sell it by the caseload, and for the most part, it will take care of just about any fish you have. So the question is, if flake food is so good, why are there other types of food? Basically because you'll buy them, but some of them do offer some advantages which may be large or small depending on what the fish is that you are trying to feed.
FLAKE
Flake is available in many different types. Though you will find a high variety in types of flake food, you will not see much difference in what the food does for your fish. Most advanced hobbyists will buy food that is high in protein, though the actual visible difference in your fish for doing so is debatable. In addition to the basic flake and goldfish flake, there are vegetarian flakes, brine flake, color-enhancing flake and other specialty flakes. Some of these flakes do offer some advantages. For example, vegetarian or Spirulinia-based flake foods are very valuable to fish that are not carnivores. Fish have different types of stomachs based on what types of diets they have in the wild. Due to those differences, a fish that is a vegetarian can literally starve to death with a full stomach if they are being feed the wrong type of food. Most of the fish in the aquarium hobby are not solely vegetarians, but many will benefit from a small amount of plant matter in their diet. It is useful to mix in vegetarian flake with the other foods that you are feeding.
Color-enhancing flake foods usually contain carotene. Carotene will brighten reds and oranges in any fish. While this is useful for many fish, especially guppies, platies, and other livebearers, many fish do not have the type of coloration that will benefit from adding Carotene to their diets. Usually if a fish has yellow, orange, or red in their natural coloration, they will benefit from some color-enhancing flake, but you will receive the same benefits by feeding it 50% of the time as you will feeding it 100% of the time, so it is worthwhile to mix it with a basic flake.
Most other specialty foods, such as brine shrimp flake, do not add much to the basic aquarium. These foods are not any better for your fish than a basic flake, but the smell of the flake may help more picky eaters be inclined to eat. However, for picky eaters, I'd recommend a freeze-dried or frozen food as they tend to have much better results than a similarly based flake food.
Be aware that all flake foods will cloud the water if they are overfed to your fish. If you don't overfed your fish, no flake food (nor any other type of food for that mater) will cloud the water.
PELLET
Pellets are broken into floating and sinking types. The floating types are usually made for large cichlids that need food of a larger size than flake. The sinking types are generally recommended for bottom feeders in tanks where the food is consumed before it reaches the bottom of the aquarium.
One of the big advantages of pellet foods is that they are generally cheaper than flake foods per oz. However, be aware that many fish, such as tetras, gourami, and other mid to top-water fish, cannot survive on a diet based on pellet foods.
I would personally recommend sinking pellet foods as a supplemental food to be feed once a day to any aquarium that has bottom dwellers such as loaches, dwarf cichlids, and catfish. In addition, there are sinking pellets that are made for vegetarians. These can be used as a valuable supplement for both algae eaters and many of the plecostomus species available.
The floating pellets are an invaluable food that can be used as the sole source of food for large cichlids such as the Oscar and many of the larger American and African cichlids. While there are smaller floating pellets that are designed for community fish, unless you can get them at a very small size, I would recommend using flake over the pellets for a general "community aquarium" as flake foods can feed a wider range of fish sizes without having to buy multiple sizes of pellet.
FREEZE-DRIED
Freeze-dried foods are often a good replacement for frozen foods for fish that either picky eaters, or that are being prepared for breeding. The hinderment is that they are usually more expensive than frozen foods, and your fish will not prefer them to frozen foods. However, many aquarists have trouble keeping frozen or live blood worms in their fridge, and so freeze-dried foods become a good alternative.
The main advantage is that a freeze-dried food will more closely resemble the fishes food in the wild. This can help some fish in an invaluable way as it will make them more likely to act like they do in the wild, and thus more likely to breed. Beyond the intrinsic value for breeding, freeze-dried foods are not really necessary, and are more of a nicety than anything; unless of course you are feeding freeze-dried tubifex worms. Freeze-dried tubifex worms are basically just a waste of time as far as foods go.
FROZEN
Frozen foods are especially valuable if you have fish that are picky eater or that you plan to breed. Almost any fish will run to a frozen food. Frozen foods are easy to keep in your freezer, they are reasonably priced if you don't have too many aquariums, and they are obviously preferred by the fish in the aquarium (in fact they can make quite a show if you have some friends over!). The only real drawbacks are that they can be smelly (though you shouldn't notice anything in your freezer), they take about three times as long to feed as flake foods, and you have the possibility of parasites if they aren't well screened before freezing.
LIVE FOODS
Live foods are basically at the end of the progressive later of foods that your fish will prefer and that provide some intrinsic value to breeding. Basically for that type of thing, freeze-dried is good, frozen is better and live foods are the best. Unfortunately, most live foods are too difficult to obtain and keep for them to be of real interest to beginners. You will find that advanced hobbyists use them on a daily basis, and that they raise many of them on an on-going basis.
Most live foods that are cultured are raised for the specific purpose of feeding young fish. Newly hatched fry will grow much quick on live foods such as brine shrimp, infusoria and microworms. I recommend microworms due to the fact that they are easy to raise. All you need is a starter culture, a piece of breed, a closed container, and some water, and you'll be able to always have a live food on hand.
For some really good information on culturing live foods, click here.
CONCLUSION
After considering all the different types of food that are available, the final question to ask is "what type of food should I use?" You should use whatever type of fish food you feel works best for you. Perhaps the best way to make sure your fish receive everything they need is to use a varied diet made up of all the different types of food available. If you are going to use just one food, I would recommend a basic flake for community fish, and a floating pellet for cichlids over 3".
As a general rule for feeding I would recommend 3 flakes per 1" of fish per day for fish 1-3", 4 medium-sized pellets per 1" of fish per day for fish 4-7". 5 Large-sized pellets per 1" of fish per day for fish 8 plus". It's a 3-4-5 rule that can help you to not overfeed, but the best rule is to pay attention to your fish and what they are eating. Remember that most fish will eat themselves to death and that underfeeding is better than overfeeding, and you and your fish will both have a better time together.