Makin' It Natural
A DIY Guide to Formulating Homemade Fish Food
By Melody P. McKinnon
The first argument we hear against making our own fish food is surely perpetuated by the pet food industry - what if we don't provide everything the fish requires? Considering most commercial food has the naturally-sourced vitamins heat processed out of them and flakes lose crucial vitamin supplements within 30 seconds of hitting the water (Pannevis and Earle, 1994), there is little doubt that we can do better if we're armed with some basic information.
What are the dietary requirements of individual fish species? Don't worry - the fish food manufacturers have very little idea either! With tens of thousands of identified species of fish in the world, the idea of each having the same dietary requirements becomes quite ludicrous. For example, the average omnivore should have 30-40% protein in their diet, with growing omnivores being provided with the upper end of the scale. Guppies have been studied specifically and fell into this range perfectly (Shim and Chua, 1986). However, growing 'Swordtails' are also considered to be omnivorous and require at least 45% protein and 6% lipid level for optimum utilization and growth (Kruger et al. 2001).
To tailor a diet to the specific species in your care, you can begin by studying their wild diet and habitat. In true hobbyist form, I am positively giddy when I find a study that happens to mention the gut contents of a wild species that I keep in captivity - the information is invaluable and the near perfect model for a captive diet. When you can't find information on the wild diet of a specific species, you can often find studies about species with similar wild feeding habits in the same location. If all else fails, take an educated guess based on what you know about the habitat and the species feeding habits combined.
The natural diet is important not only to determine nutrient requirements, but also to determine the species' capability of digesting various dietary items. The wide range of intestinal morphology can be determined in a lab, but the species' digestive system evolution has also been based upon the food available in its habitat and how those food sources are combined (i.e.: Microorganisms residing in algae). I have theorized that the latter is one of the main issues with some Cichlids who are highly prone to digestion problems. The digestive system of the same species can even vary according to location (Eugenia Zandonà, 2010). Another environmental factor is the mineral content, as fish absorb minerals such as calcium from their environment (Phillips et al., 1959).
When formulating aquatic pet food, I focus on the nutritional content of the native diet and replicate it with what I have available to me, keeping in mind what is, or is most likely to be, bio-available to fish. There may be obscure requirements that we don't know about which are found in the wild foods, so it is important to simulate as closely as possible.
I can think myself to be well educated in regards to fish nutrition, but unless I have species-specific details, I am not formulating their ultimate food. The details are often in the observant minds of those most experienced with the species in question. When Jim Langhammer advises us to watch the protein intake of Goodeid females to avoid killing our brooders with super-sized fry, we can safely assume it is a fact. While no hobbyist is above being questioned, we soon learn who we can trust for educated opinions, and who just has an opinion (or is parroting someone else's opinion, possibly inaccurately). We also have to watch for commercial hype, often disguised as fact and wrapped in big words meant to impress the average hobbyist. Educate yourself and don't let them intimidate you.
If the individual species requirements aren't enough to boggle the mind, wait until you factor in breeder objectives & goals! There are many nutrients that can improve size, finnage, brood size... just about everything can be impacted by a proper diet. We also have special concerns with captive fish, including a metabolism and breeding schedule that is always in high gear. Most of us do not provide climate cycles, facilitate diapauses, etc. Then there's immunity enhancement, color enhancement, bioavailability (which can vary depending on the species)... fish nutrition is a huge picture of many diagrams.
The following information will provide you with a basis on which to begin formulating your own natural aquatic pet food.
When using items intended for human consumption in our homemade fish food, there are a few important facts to keep in mind:
- Size consideration is crucial when adding vitamin/mineral supplements and it is one of the most common mistakes made by those who make their own fish food. Most of our fish are smaller than our hand - not only are human supplements easily overdosed, but they are also inappropriately balanced. The risk of hypervitaminosis is based on fat soluble vitamins, A, D, E and K. While it is not a huge risk through natural sources, the synthetics can quickly add up when based on human requirements. For comparison, a 15 pound dog should only receive 10% of an adult human vitamin!
With a variety of naturally sourced nutrients provided and a good knowledge of the species in question, supplementation probably isn't crucial (with the possible exception of stabilized vitamin C), but I like the insurance. A few synthetic supplement sources are bio-encapsulated frozen fish food, high quality commercial food, liquid fish supplements, or baby vitamins.
- Garlic is an amazing addition and it should be crushed to provide its most active component: Allicin. It can, however, be overdosed. Garlic can irritate the mucus membranes and digestive system. Allicin is heat sensitive, so add it to a cool mixture and don't rely on heat processed food to provide it.
- Extreme caution should be used with the addition of herbs. After years of experimenting, I'm still not comfortable suggesting the use of specific herbs because there are just too many variables and too much room for error. They do not always work in the same way they do in mammals, and they can be deadly. Rosemary has, however, become an accepted natural preservative for use in both fish and mammal pet food.
- Terrestrial plant nutrients are not as bio-available to fish, basically due to cellulose binding and in some vegetables, high starch/carbohydrate content. Avoid or limit high carbohydrate foods such as corn, sweet potato, parsnips and bananas. The most efficiently utilized vegetation is aquatic vegetation, and the most nutritionally complete aquatic vegetation is seaweed/algae. The value is in the bio-availability and most importantly, the complete and concentrated nutrition that seaweed offers (boasting more bio-available vitamins and minerals than any other class of food, in fact). Individual seaweed species have various functions that they excel at, so a variety in either fresh or dehydrated form will cover all bases. Some of seaweed's medicinal qualities include anti-bacterial, anti-fungal, anti-parasite and anti-inflammatory properties (which garlic also offers).
- Many homemade foods are gelatin-based but gelatin should be used sparingly. Too much gelatin will fill the fish without providing balanced nutrients. The seaweed extract Agar may be used as a gelatin binder and it doubles as a rich source of calcium. Other binders I use include green pea & other vegetable based flours and sometimes a bit of oatmeal infant cereal.
- Organics offer reassurance and are relatively easy to find. Sometimes pesticides cannot be entirely removed even with washing, so it is a worthy investment.
- Excessive amounts of raw seafood may cause a deficiency in Thiamine. Also, any meat you purchase has passed inspection based on the assumption that the meat will be cooked, far removing it from live and freshly killed prey in that respect. Cooking items to the minimum temperatures required to make it safe for consumption doesn't even compare to the extreme temperatures that ingredients are exposed to repeatedly in commercial fish food processing.
- Eggs should always be precooked.
- Rapid growth is not necessarily healthy growth. Although protein can greatly increase growth rates, it must be accompanied by enough other nutrients to maintain the rapid pace and produce a healthy fish. Excess protein in the diet will also be excreted as ammonia into the water column.
- It is very important to balance energy sources (i.e.: lipids) and protein for healthy growth. If energy sources are lacking, protein is used for energy which sacrifices growth. If too much dietary energy is supplied it can reduce feeding and result in too little protein being ingested, resulting in an imbalance of nutrients that are stored as fat.
- Many nutrients work together synergistically, and in fact some nutrients cannot work at all without each other.
- A water supply that is low in minerals and trace elements results in an increase of dietary requirements, as fish absorb a portion from the environment. It has been my experience that Livebearers respond very well to calcium in the water supply as well as in their diet, so I supplement both.
- Color is only one indicator of good health - color enhancers and even growth can give the illusion of supreme health when the diet is actually lacking.
- Homemade foods should be fed sparingly and care should be taken to remove uneaten portions as soon as possible. 'Real' food breaks down quickly and can foul the environment. Fish won't require nearly as much of it to surpass a processed food diet anyway. Depending on your current maintenance schedule, you may have to step it up.
- To avoid waste, small food is the ticket for small fish. Instead of chopped ingredients, pureed and bound will better serve the purpose. You can also use freeze-dried vegetable powders for convenient, highly nutritious ingredients that double as a binder/thickener. Powdered ingredients also fill the otherwise nutrient-poor gelatin with nutritious food. It won't foul the water column like the 'juice' from whole ingredients will and serves the purpose of sponging up these liquids for the fish to ingest.
- Ingredients you may want to avoid/limit due to dietary unsuitability or their potential to quickly foul the environment are mammal fat, oily fish, high food chain fish, foods high in phosphates, fruit, legumes, oilseeds, raw starch, high-carbohydrate garden vegetables (corn, sweet potato, parsnips, etc.), anything with added salt, dog/cat food, and fruit or vegetable juice.
The nutrient table below will give you a general idea of the nutritive requirements of your fish, why they require it and some of the ingredients I use to get it into them. I have tried to be as specific as possible (i.e.: I have named specified seaweed species that are noted as exceptional sources of specific nutrients, even if all seaweed species contain that nutrient). I recommend all live, fresh, frozen, freeze-dried or low-heat dehydrated ingredients - to do otherwise defeats the purpose.