December 05, 2020

First things first.

A bunch of you had asked me further about the idea I brought up recently in our piece on Kuhli loaches, about pre-stocking" an aquarium with food for your fishes before you add them. You wanted more specifics.

Okay, cool. Happy to accommodate. Of course, I need you to do a little exercise, first:

You're a fish.

Seriously. Make yourself a fish...for a second. (I think I'd be a Black Ghost Knife, FYI. What, you thought I'd be a Cardinal Tetra or something? Really? Sheesh!)

Would you like to move into a house which didn’t have a refrigerator full of food? I wouldn’t, for sure. Unlike humans, fishes seem to have not lost their "genetic programming" for grazing and hunting for food. Let’s face it—most of the waking hours of aquatic animals are devoted to acquiring food and reproducing. They need to have some food sources available to "hunt and graze" for.

That’s reality.

So why not help accommodate our your animals’ needs by supplementing their prepared diet with some “pre-stocked” natural foods in their new home? You know, slow down, get things "going" a bit, and then add the fishes?

I’m not talking about tossing in a few frozen brine shrimp hours before the first fishes go in the tank—I’m talking about a deliberate, systematic attempt to cultivate some living food sources within the system before a fish ever hits the water! Imagine a “new” system offering numerous foraging opportunities for it’s new inhabitants!

in our world, that might mean allowing some breakdown of the botanicals, or time for wood or other botanicals to recruit some biofilms, fungi- even turf algae on their surfaces before adding the fishes to the aquarium.

“Scott. You’re being impractical here! It could take months to accomplish this. I’ve just spent tons of money and time setting up this tank and you want me to deliberately keep this tank devoid of fishes while the biofilms form and Daphnia reproduce?”

Yes. Seriously.

I am a bit crazy. I’ll give you that.

Yet, with my last few systems, this is exactly what I did.

Why?

Well, for one thing, it creates a habitat for sighs which is uniquely suited to their needs in a different way.

Think abut the way most fishes live. They spend a large part of their existence foraging for food. Even in the cozy, comfortable confines of the aquarium.

So, why not create conditions for them which help accommodate this instinctive behavior, and provide opportunities for supplemental (or primary!) nutrition to be available to them by foraging.

Now, I have no illusions about this idea of "pre-stocking" being a bit challenging to execute.

I’m no genius, trust me. I don’t have half the skills many of you do but I have succeeded with many delicate “hard-to-feed” fishes over my hobby “career.”

Any "secret" to this?

None at all. I'm simply really fucking patient.

Success in this arena is simply a result of deploying..."radical patience." The practice of just moving really slowly and carefully when adding fishes to new tanks.

A really simple concept.

I mean, to some extent, we already deploy this practice with our blackwater/brackish, botanical-style tanks, right? The very process of creating a botanical-style aquarium lends itself to this "on board supplemental food production" concept. A sort of "food web" that's pretty analogous to those found in Nature, right?

And one of the most important functions of many botanically-influenced wild habitats is the support of food webs. As we've discussed before in this blog, the leaf litter zones in tropical waters are home to a remarkable diversity of life, ranging from microbial to fungal, as well as crustaceans and insects...oh, and fishes, too! These life forms are the basis of complex and dynamic food webs, which are one key to the productivity of these habitats.

You can do this. You can foster such a "food web"- or the basis for one- in your aquarium!

Wait a minimum of three weeks—and even up to a month or two if you can stand it, and you will have a surprisingly large population of micro and macro fauna upon which your fishes can forage between feedings.

Having a “pre-stocked” system helps reduce a considerable amount of stress for new inhabitants, particularly for wild fishes, or fishes that have reputations as “delicate” feeders.

And think about it for a second.

This is really a natural analog of sorts. Fishes that live in inundated forest floors (yeah, the igapo again!) return to these areas to "follow the food" once they flood. In fact, other than the physical flooding itself, this pursuit of food sources is the key factor in the migration of fishes into these habitats.

In the aquarium, it's not all that different. Our systems are built on the process of decomposition and fostering microbial growth. It's a foundation of the botanical-style aquarium approach. Far different than the "typical" approach to starting an aquarium, which is really more reliant on filtration, external food inputs (from us!), and the execution of consistent maintenance to get it through the "startup" period, when a typical system is almost "sterile" compared to our botanical-style ones.

And the "waiting period" isn't all that long.

It just takes a few weeks, really. You’ll see fungal growth. You'll see some breakdown of the botanicals brought on by bacterial action or the feeding habits of small crustaceans and fungi. If you "pre-stock", you might even see the emergence of a significant population of copepods, amphipods, and other creatures crawling about, free from fishy predators, foraging on algae and detritus, and happily reproducing in your tank.

We kind of know this already, though- right?

This is really analogous to the tried-and-true practice of cultivating some turf algae on rocks either in or from outside your tank before adding herbivorous, grazing fishes, to give them some "grazing material."

Radical patience yields impressive results.

I realize that it takes a certain patience- and a certain leap of faith-to do this. I’ve been doing it for a while and I can tell you it works.

If you like delicate or difficult-to-feed fishes, or even if you simply want to try something a bit different "just because", it’s a technique that could help you succeed where you might have failed in the past with some species.

The point of this practice is pretty simple. Embrassingly so, actually: To help develop—or I should say—to encourage the development and accumulation of some supplemental natural food sources in the system before they are quickly devastated by your fishes.

It's kind of the "refugium" concept yet again.

And it's not all decomposing leaves and twigs and stuff that helps accomplish this- in Nature and I the aquaruum.

One of the important food resources in natural aquatic systems are what are known as macrophytes- aquatic plants which grow in and around the water, emerged, submerged, floating, etc. Not only do macrophytes contribute to the physical structure and spatial organization of the water bodies they inhabit, they are primary contributors to the overall biological stability of the habitat, conditioning the physical parameters of the water.

Of course, anyone who keeps a planted aquarium could attest to that, right?

One of the interesting things about macrophytes is that, although there are a lot of fishes which feed directlyupon them, in this context, the plants themselves are perhaps most valuable as a microhabitat for algae, zooplankton, and other organisms which fishes feed on. Small aquatic crustaceans seek out the shelter of plants for both the food resources they provide (i.e.; zooplankton, diatoms) and for protection from predators (yeah, the fishes!).

Of course, leaves are a huge and important component in the construction of a food web.

Decomposing leaves will not only provide material for the fishes to feed on and among, they will provide a natural "shelter" for them as well, potentially eliminating or reducing stresses.

And the possible benefits to fish fry are interesting Gand important, IMHO.

In Nature, many fry which do not receive parental care tend to hide in the leaves or other biocover in their environment, and providing such natural conditions will certainly accommodate this behavior.

Decomposing leaves can stimulate a certain amount of microbial growth, with infusoria and even forms of bacteria becoming potential food sources for fry. I've read a few studies where phototrophic bacteria were added to the diet of larval fishes, producing measurably higher growth rates. Now, I'm not suggesting that your fry will gorge on beneficial bacteria "cultured" in situ in your blackwater nursery and grow exponentially faster.

However, I am suggesting that it might provide some beneficial supplemental nutrition at no cost to you!

I've experimented with the idea of "onboard food culturing" in several aquariums systems over the past few years, which were stocked heavily with leaves, twigs, and other botanical materials for the sole purpose of "culturing" (maybe a better term is "recruiting) biofilms, small crustaceans, etc. via decomposition. I have kept a few species of small characins in these systems with no supplemental feeding whatsoever and have seen these guys as fat and happy as any I have kept.

And it's the same with that beloved aquarium "catch all" of infusoria we just talked about...These organisms are likely to arise whenever plant matter decomposes in water, and in an aquarium with significant leaves and such, there is likely a higher population density of these ubiquitous organisms available to the young fishes, right?

Now, I'm not fooling myself into believing that a large bed of decomposing leaves and botanicals in your aquarium will satisfy the total nutritional needs of a batch of characins, but it might provide the support for some supplemental feeding! On the other hand, I've been playing with this recently in my "varzea" setup, stocked with a rich "compost" of soil and decomposing leaves, rearing the annual killifish Notholebias minimuswith great success.

It's essentially an "evolved" version of the "jungle tanks" I reared killies in when I was a teen. A different sort of look- and function! The so-called "permanent setup"- in which the adults and fry typically co-exist, with the fry finding food amongst the natural substrate and other materials present I the tank. Or, of course, you could remove the parents after breeding- the choice is yours.

So, what would some candidate organisms be for "pre-stocking" a botanical-style aquarium?

How about starting with (okay, sounding a bit commercial, I know, but...) the versatile Purple Non Sulphur Bacteria (PNSB), Rhodopseudomonas palustris- the species which forms our product, "Culture." PNSB are useful for their ability to carry out a particularly unusual mode of metabolism: "anaerobic photoheterotrophy."

In this process, they consume organic wastes while inhabiting moderately illuminated and poorly oxygenated microhabitats (patches of detritus, leaf litter beds, shallow depths of substrate, deeper pores of expanded clay media, etc.). In addition to helping to maintain an ecologically stable microhabitat, "Culture" provides a nutritious live food source for zooplankton as well as soil mesofauna.

Yeah, these guys form the "foundation" of your food chain!

Next, perhaps some "starter cultures" of organisms like Paramecium, Euglena, etc. You know, "infusoria" from the old school aquarium literature. And then, small crustaceans like Daphnia, and copepods of various types.

Pure cultures of all of these organisms are available online from various biological supply houses. They're a fantastic source of biodiversity for your aquarium!

Of course, the more daring among you may want to introduce various worms, like "Black Worms" or Tubifex worms, if you can find clean cultures of them. For that matter, even "blood worms", which are actually the larval phase of the midge.

Some organisms, such as nematodes and chironomids ("Bloodworms!") will dig into the leaf structures and feed on the tissues themselves, as well as the fungi and bacteria found in and among them. These organisms, in turn, become part of the diet for many fishes.

In the aquarium, just like in Nature, some organisms, such as nematodes and chironomids ( those damn Bloodworms again!) will dig into the leaf structures and feed on the tissues themselves, as well as the fungi and bacteria found in and among them.

These organisms, in turn, become part of the diet for many fishes.

Food Web.

And the resulting detritus (here we go again!) produced by the "processed" and decomposing plant matter is considered by many aquatic ecologists to be an extremely significant food source for many fishes, especially in areas such as Amazonia and Southeast Asia, where the detritus is considered an essential factor in the food webs of these habitats.

It performs the same function in an aquarium- if we allow it to.

And of course, if you observe the behavior of many of your fishes in the aquarium, such as characins, cyprinids, Loricariids, and others, you'll see that, in between feedings, they'll spend an awful lot of time picking at "stuff" on the bottom of the tank. In a botanical style aquarium, this is a pretty common occurrence, and I believe an important benefit of this type of system.

When you start seeing your fishes "graze" casually on the materials that pop up on your driftwood and botanicals, you start realizing that, although it might not look like the aesthetics we have had in mind in years past, it is a beautiful thing to our fishes!

You can do this.

And, as a lover of the botanical-style aquarium, you're at the forefront of the art and science of creating functional food webs within the aquarium. And it all starts with patience.

First thing first.

Stay patient. Stay studious. Stay excited. Stay curious. Stay bold...

And Stay Wet.

Scott Fellman

Tannin Aquatics