top of page

Feeding an Aquarium

●     The three types of foods are pellets, flakes, and frozen mixes, each with their own advantages

●     It is best to use a variety rather than relying on a single product

●     Do not overfeed: this is the downfall of most mismanaged tanks

●     Freshness is important.  Food loses its nutritional value and can even get toxic as time goes by. 

●     Refrigeration/freezing helps preserve food



An appropriate diet is important for maintaining healthy fish( and some corals). While there are many fish foods (flakes and pellets and frozen mixes) which claim to be a “staple” and contain everything needed to maintain the health of fish, the reality is that we don't know exactly what is necessary to keep fish healthy. Feeding a variety of things increases the chances that your fish will consume their essential nutritional needs.


Feeding fish:

There are a few new fish feeds which are close to 100% absorbed and in a fish only aquarium this may be important because any non-digested waste ends up in the system as poor water quality which, depending on lighting, could also mean increased algae growth or need for water changes. In a healthy reef, the extra material likely gets incorporated somewhere by micro-organisms. New Era line is one of these highly digestible foods.


Feeding a single type of fish food is extremely common but think about if you ate nothing but apples for your entire life. Now consider that those apples had been on the shelf for 6 months. Food that has been sitting on the shelf (or even in the freezer) for months often leads to fish goes bad. If fed continuously it can lead to your fish becoming nutritionally compromised and  disease becomes more likely. Flake and pelleted food, even when still sealed in their packaging, lose nutritional value over time. Omega 3 fatty acids and vitamins prone to breaking down, like vitamin C, disappear from food at room temperature long before the majority of it is used. Keeping fish foods in the refrigerator or freezer slows down degradation however ideally you feed out all of your pelleted and flake foods within a few months of opening them.


Most of processed fish foods have had a nutritional analysis done on them which will tell you the total protein.  While most companies will say that these are generally accepted as nutritionally complete, again scientists really have no idea for most ornamental fish. There has been research in growth for things like catfish, tilapia, salmon, and other farmed fish because it was in the financial interest of producers to understand the energy and nutritional requirements of these fish to maximize their growth and health .


That said, if you are giving them a variety of good, be careful about the quantity.  A fundamental of keeping aquariums is not to over feed. It's the #1 reason for established tanks failing. It can be offset with water changes and to an extent chemical filtration and skimming, however, if you have heavy algae growth, 99 out of 100 times is from excess nutrient in the water from feeding.


Fish need a lot less food than we think they do. It is not evil to keep them at a certain size in our aquariums as in nature they have indeterminate growth...they continue to grow their entire lives (though slower when older). There is no set rule for feeding but if your fish are obviously fat from a feeding more then once every three days, you are feeding too much. If you have a fish which is a food hog, different size/types of food can be offered to avoid this fish getting all of the food. The food can also be put into the tank all simultaneously so that most fish can eat from a “snow globe” effect.

You are probably feeding too much if:

•         There is still food after 1 minute in anything but a huge established reef tank, you are probably feeding too much.

•         You have algae problems

•          There are any level of phosphates and nothing has died

•          The corals aren't looking happy and your nitrate, kH, and Calcium are good.


Pellets & Flakes

As a beginner, a pelleted food from ocean nutrition, tetra, or Thera spectra is fine so long as you keep it in the freezer. Higher protein on the label is in almost every case better. The exception is a plant based diet for herbivores like algae wafers or ocean nutrition's formula 2 diet where nobody knows if it might be better but it's likely to provide herbivorous fishes with appropriate nutrients because it's what they eat in nature. If you have a variety of fish or are heavy on herbivorous fish (tangs foxfaces blennies etc. it's probably important to either supply these as part of the food that goes in, or give them real algae (nori or equivalent dehydrated seeweed).


These can be used ideally for three months so there is no need to buy the jumbo size for your 30 gallon tank. Also, most processed foods have expiration dates labeled. Generally this is based on room temperature and ideal humidity. It will not give you an accurate idea of if the food is still rich in vitamins and fatty acids which degrade over various amounts of time but is a pretty good index of the earliest point that food may become rancid and potentially dangerous to feed to your fish. A quick and dirty test is to smell the food and if it still smells sour or potent, or doesn’t smell at all because it is stuck together, it’s time for new food.


Pellets are generally cleaner for a tank (more ultimately goes into a fish´s stomach) however if you have a variety of mouth sizes, such as the planktivorous chromis’ and anthias or a variety of little gobies and blennies, the flakes ability to accommodate all (even the inverts searching out scraps) is necessary. Also, a large pellet in the mouth of a puffer or trigger can make a mess as they use pharyngeal jaws to crunch it and lots of crumbs come out of their gills. Medium pellets that fish swallow completely in one bite are ideal.


For flake and pellet foods in our quarantine we use Prime reef flake, formula 2 pellet, and discus flake (for freshwater) and these can be obtained for the cheapest online (usually from Drs Foster and Smith).


Frozen mixes

As a complement to pellets/flakes, you can add an appropriate amount of a frozen mix of food such as H20 life 50/50 mix or Sally’s brine shrimp enriched with omega or spirulina (regular brine shrimp is practically worthless nutritionally to fish yet for some reason so many pet stores offer it, recommend it, and have people feeding it)


A reasonable option for any fish is buying fresh seafood and chopping it up as needed or in batches (kept in an ice cube trays for the week for example). Some fish will wean much faster on things like scallop or cocktail shrimp than anything sold as frozen fish food. Most supermarkets have a frozen blend of something like shrimp, squid, clam, and scallop and you can take the whole bag and blend it up, even adding basic gelatin to hold it together better, and set yourself up for a month of feeding a large amount of fish for substantially less than using those tiny prepackaged cubes designed for aquariums.


Similarly most supermarkets and definitely asain food markets will carry dehydrated seaweed in flat mats for making sushi. It is called nori in japanese but usually is a species of Ulva algae. It is important when buying this to make sure that it is not flavored with soy or spices, the fish don't like this and it makes a mess in the tank. For about 5 times the price, various companies have dehydrated Ulva and a few other types of algae and packaged them for use as aquarium fish food which is good but expensive.


Frozen mysis shrimp and bloodworms are healthy items used regularly to feed more finicky marine fish but those little cubes get expensive quickly. Again, we recommend to only use frozen brine shrimp if they are enriched with omega-3 or spirulina. Even still these brine mixes are low value energetically. Products from H20 life (white package) and some from ocean nutrition/San Francisco Bay company are the most common and there are good options for diversifying your fish’s diets from each company. Piscine Energetics mysis is good for beefing up fish but also makes a mess ( a protein skimmer will often overflow). It is also too large for smaller fish like mandarins.


Live foods from salt water can harbor parasites and really should be avoided. Live cultured copepods, rotifers, and green water have not commonly caused problems but there is uncertainty in these cultures. Live mysis or grass shrimp have caused a number of problems when added to tanks with parasitic disease. Fish such as lion fish and ribbon eels should be fed only freshwater live fish and only temporarily as a means for weening them onto frozen marine food. Lion fish fed goldfish accumulate indigestible parts in the stomach and gi tract and become constipated. Fresh water grown foods fed to salt water animals also may create enzyme and vitamin deficiencies; a common case is thiamine deficiency. Live brine from pet stores is notorious for carrying uronema, pathogenic Vibrio sp. of bacteria, as well as many other bad disease causing agents. If you must use them to ween something like a mandarin goby or seahorse (the brine must be enriched and can only sustain them temporarily as it's nutritionally empty) it is important to rinse it off under flowing fresh water in a net for a minute or so to hopefully dislodge parasites and reduce bad bacteria. Also, if it must be used, ideally it is fed in a quarantine tank where if disease emerges it might be treated more effectively. Below is a guide to weening tough to feed fish from their natural food sources.


A few notes on finicky eaters:

•         Some fish such as moorish idols and copper banded butterflyfish may not eat initially because they are in too small of a tank, intimidated by neighbors, or just don't understand the process of eating in an aquarium. The best way to get them to eat is to offer small amounts of a variety of different looking natural foods. Frozen mixes, seaweeds, and things strait from the supermarket such as clam on the half shell or shrimp still with legs are a good option.

•         Weening seahorses, pipefish, and mandarins can be a challenge. Live brine ( rinsed as mentioned before) , live blackworm, or live mosquito larvae can be used initially but the goal is to get them eating frozen food (and wth mandarins even pellets) as soon as possible. The best way which has worked for us is actually very well described in this article which appeared in coral magazine a few years ago.

•         Weening lionfish, groupoer, angler fish, or eel is more easy.

◦          Start with feeding them a guppy, tuffy, or killifish (whatever is mouth size appropriate) each day until they get used to eating that food...usually three days.

◦          Then, using a wire hook the live fish through the tail and bring it down to the predator trying not to scare it. Do this until it becomes accustomed and chases the wire to the surface or eats at the surface.

◦          Then put frozen food on the wire of about the same size and feed that at the surface.

◦          Finally, the fish just starts to eat whatever hits the surface when you are looming around.

◦          Don't even bother with ribbon eels. Their survival rate is tragic. They need sand or rubble with tubes, hunt live mysis initially if you are extremely lucky, and are more difficult to wean than anything in the hobby.

◦          Orange spotted filefish can be weened though it is a long process described here


Feeding invertebrates:

Generally inverts are not finicky eaters and in most tanks the species which are kept are durable clean up crew type animals. It's necessary if you have herbivorous animals such as most sea urchins to actually have algae in the tank or be supplying that to them regularly. A few key things to be aware of with feeding inverts:


◦          Harlequin shrimp can never be weened from eating starfish.

◦          Keeping clams of the tridacnid family (giant clam types) requires reef type lighting as most of their nutrient comes from symbiotic algae, similar to corals.

◦          Filter feeding organisms such as sea apples (type of sea cucumber) and flame scallops need to be in a well established reef or need to be supplemented with plankton which often greatly pollutes anything but a well established reef. Therefor, these animals are not recommended for newer reef tanks or fish based tanks.


Feeding Corals

Almost all photosynthetic corals in a well established tank do not need to be fed a supplement. They derive what they need from output from the tank (worm eggs, snail mucus, microscopic crustaceans, sponge cells, etc.). Provide light and good water chemistry and a bit of food to the resident fish and nature takes care of itself. There are a few species of coral, specifically the large polyp stony corals (anything with a mouth you can see) that appreciate supplementary feeding and will be healthier and grow faster if fed. Be careful with this as any nutrient that goes into the tank will be incorporated into the system and if it's not taken up fast by the good stuff (corals, other invertebrates, good macro algaes) it ends up as nitrates and phosphates which cause corals to close up and encourage algae and cyanobacteria growth.

bottom of page