Guess what's coming to dinner...?

Do you ever wonder what many of our favorite non-herbivorous aquarium fish species eat in the wild? I mean, what they tend to graze on all day? 

Well, interestingly, a lot of what they eat are insects. Yeah, lots and lots of 'em. And a few other things, like fish eggs and Daphnids.

A partial excerpt from rom Walker, in his paper "The Food Spectrum of The Cardinal Tetra (Paracheirodon axelrodi, Charicidae) In Its Natural Habitat" gives us a look at what was found in the gut content analysis of a number of specimens collected in Amazonia:

"...Most Cladocera appeared to be of the small, almost spherical type Moinidae(?), however, larger daphnids and some macrothricids also appeared. The Copepoda were mostly the benthonic Harpacticidae. Other insects include mostly Ephemeroptera nymphs, Ceratopogonidae and other Diptera larvae, smallest adult flies or pupae with already pigmented eyes (Dolichopodidae?), small Coleoptera larvae, Hemiptera nymphs (Naucoridae?) and chewed-up adult ants.

This last item indicates that prey is also taken from the water surface, such as emerging adults (small flies) and insects that fell on– or were swept into – the water. Doubtless, some of unrecognizable insect fragments were the remains of ingested chironomid pupae or adults. 

Other prey are small oligochaetes and mites (Oribatidae?). Uncertain is the suggestion of newly hatched shrimps on three occasions, and of a fish larva. Mesofauna  includes Rotifera, usually several individuals per stomach, and of Thecamoebae ( including Difflugiidae, Nebeliidae and Arcellidae). Eggs appeared generally to be of invertebrate origin, probably of Microcrustacea, but on two occasions vertebrate eggs (probably fish) were found."


So, why do we tend to feed our fishes stuff like brine shrimp, pellets, and other substitutes? Wouldn't it make more sense to feed more of stuff like bloodworms, Daphnia, wingless fruitflies, glassworms (midge fly larvae), copepods, fish eggs, mosquito larvae and even ants- as these are far, far more "realistic foods" than brine shrimp? I love brine shrimp, feed it a lot, and have absolutely nothing against it. And I get it in part, because these foods are easy to procure, manage, etc. Convenience is huge in our busy lives. I totally get that.

However, one can't help but wonder if fishes would be healthier, develop more quickly, and just overall do better when fed foods more similar to what they would consume in nature. Right? 

I'm thinking it makes more sense.

I mean, we go to such great lengths to meet the needs of our fishes and plants, culturing more "appropriate" live foods couldn't be that much more of a pain in the ass than say, following a fertilization regimen in a planted tank, or managing mouth brooding cichlid eggs, or...Well, you get it.

Another bad analogy- Wouldn't it be better eating a serving of fresh fruits, nuts, etc. than you would a candy bar that has flavorings or precursors derived from these foods in it? I mean, the whole "fresh food" versus "processed" food thing, right?

Now, I realize that some of these foods are harder to procure (like glassworms), potentially problematic/scary to collect/culture (mosquito larvae...hello, Zika scare!), and expensive (the cost of live copepod cultures can add up). However, when I think about what it would be like for captive fishes to be fed foods with a nutritional profile, taste, and attractiveness extremely similar to what they are "genetically programmed" for, it makes me curious...

Might they do just that much better if provided truly natural foods? Or at the very least, more realistic "surrogates?" 

A century on in the modern aquarium hobby, I'm sure we can do a bit better than just brine shrimp, right?

More realistic "surrogates" would be stuff like little winged insects and flies...I know you're thinking about how impractical it would be to go around the house swatting at gnats and fleas and stuff to feed your fishes. No argument. However, would culturing say, wingless fruitflies be that bad of an idea? And feeding more frozen bloodworms? Notice I said "frozen" bloodworms?

(Ok, I'm not personally sold on freeze dried anything. And I am no expert on this at all, so it's purely based on emotion. It's one thing if these items are included in say, a pellet. Quite another if you're literally freeze drying the food item and feeding it. I could be totally wrong, of course- but I'm digressing here. We're talking about the idea of "fresh" foods...)

It's something to think about yet again. Feeding our fishes. Or should I say, what we feed our fishes. Although it's seemingly a well-trodden topic, I think there is more there. Just think about the marine side of the hobby for a second.

Although many factors contributed, we really started to see some success with spawning and maintaining more "finicky"marine fishes over the long haul when we were able to come up with more natural, species-appropriate foods for them.  Oh, and I didn't even mention the success garnered when we started feeding corals correctly...yeah. Obviously, we're much further along in the freshwater game, yet perhaps it's time to re-think this topic just a bit more; look at it with fresh eyes? Something for hobbyists and enterprising startup fish food manufacturers to contemplate, IMHO. 

Oh, and to leave you blackwater fans with one more bit of unrelated "food for thought", I offer this little tidbit from a friend who has done some intense research into the health benefits to fishes of humic substances in aquariums ( yeah, blackwater...).

He's poured over scholarly work during the last few years and came up with a lot of interesting stuff. This conclusion that he forwarded to me from a study on the affect of these substances on the health of fishes, however, is really cool:

"It appears that dissolved Humic Substances have to be considered abiotic ecological driving forces, somewhat less obvious than temperature, nutrients, or light."

As my friend has been claiming, humic substances are to fish, "...a foundational necessity, ranking up their with temperature and food."

BOOM! Chew on that one for a while.

Perhaps while you contemplate more leaves for your next blackwater aquarium?

So much happening in our little "tinted" world as we head into Fall. That time of year I like to call "aquarium season" is just getting underway!

So, contemplate these little tidbits I foisted on you today. Consider if they would make any difference in say, that one pesky fish that's resisting your spawning efforts. Or that tough-to-acclimate wild fish...Or simply, your school of Cardinal Tetras!

Stay curious. Stay inquisitive. Stay innovative. Stay creative.

And Stay Wet.

Scott Fellman

Tannin Aquatics



Scott Fellman
Scott Fellman


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