Nature vs. Nurture

[skylsdale]

I've been in the hobby for quite a few years now, and as of late my interest has shifted toward the subject of biotope aquaria. When researching many of the habitats, you realize that most waterways and aquatic environments are not the ideal planted utopias that many of us recreate in our systems. Actually, many of them tend to be pretty rank in comparison.

Only recently have I started to get somewhat interested in keeping discus, and there seems to be a big paradox in the environment they come from compared to the ones we create for them. Down in the biotope forum there are a great bunch of photos taken by Takashi Amano of a small blackwater igape and what it looks like beneath the surface--quite a bit different than what most people realize. While their ranges change based on the water level, the environment is much more bare than people realize.

I'm sure this has been discussed here before, but I'd like to start a little discussion on people's thought regarding the conditions discus in the wild face and how that translates into our tanks. For years discus have been thought of as an incredibly fragile fish, which is one of the reasons I have not attempted them. But keeping them has proven that they can actually do well in varyious pH's and water conditions.

One thing I notice is the sheer sterility that people strive for in their discus tanks. I often read that this is to prevent parasitic infections, illness, etc. With the paranoia over keeping such pristine tanks, I have to wonder if wild discus are absolutely overrun with parasites and infections in their natural environment? Are there mass dieoffs caused by illness in the wild? Are they really that fragile, or is it somehow amplified in our tanks and their immune systems mysteriously shut off, rendering them open to all sorts of disease? Many of these fish come from pretty turbid waters--I can't imagine they are as delicate as many report them to be. What do you all think?

Personally, I prefer the coloration of wild discus over the selectively bred cobalt camo twin turbo-powered "it slices and dices" mutations that crowd the market. I have also read a few past threads on here where hobbyists get a few wild fish and are amazed at the personality of these wild specimens. The fish actually hunt for food in the driftwood and appear more brazen than their captive bred counterparts. Are they hardier as well...more resistent to disease? Is something being lost in the countless generations of discus being bred in captivity?

Again, this thread is intended for the sole purpose of discussion and civil debate. I'm interested in hearing what you all have to say.

[Ralph]

Great post!
It is funny that the closest thing we have to a real discus biotope is a barebottom tank! I'm talking about the lack of aquatic plants in parts of the Amazon and also about the water changes. With the water changes we are really reproducing what happens in their natural habitat. But instead of the river taking away their waste products, we do it with WCs (or at least dilute them).
Most of the show tanks that you see aren't really attempts to reproduce discus environs, we mainly just like the look of the plants and driftwood. But that is valid, a true biotope is very difficult to create, unless you happen to live in the area. We are working on it in the Biotope section though. We have a series of interviews coming up shortly (I hope) of people who have spent time on the river. The main purpose is to get a better understanding of the specifics of where wild discus live. But it should be an interesting read for anyone who admires the King of the Aquarium.

As far as the reputation of discus as hard to keep, it is really a question of the rate of success. You may be able to keep a school of discus alive under "tetra conditions" (rare WCs, tap water, low temps, flakes only, etc.) and people have done that. But you chances of having healthy, large fish is increased by doing all the extras that they talk about (endlessly) on the forum. And when your fish cost $40 to $100 US, most people are willing to do just that. I've never seen figures for it, but my guess is that the survival rates to adulthood for discus in the wild are minuscule compared to say, a professional breeders tank (even with the cull rate). Typically in the wild, any animal that has 200 to 300 offspring (eggs anyways) is doing well if two or three actually survive to have their own offspring.

[skylsdale]

Thanks Ralph. I did see a mention on the upcoming articles you mentioned and hope to see them soon. In all honesty, my "ideal" discus system is a dimly lit tank with a sandy bottom and dense network of branches and tree debris. Based on what I've read on this board, it seems next to impossible to maintain a tank like this. IMO, it's much more fantastic to see how their shape and form allow them to inhabit the narrow spaces found in submerged trees and bushes, rather than glide through the expanses of a bare tank. Again, just my opinion...

I guess another question is why discus seem so much more temperamental to keep than other fish species from the area? Being subject to the same conditions, you would think that other species such as cardinal tetras and Nannostomus spp. would need constant water changes and be extremely prone to parasitic infections.

Also, what about the issue of wilds vs. captive breds? I'm interested to hear opinions on that as well.

[Ralph]

The tank you describe is very close to where I am heading. Certainly not a tank for everyone but it is one of those "eye of the beholder" things. I'm at halfway point now, I'm working on a tank with no substrate, just plants on driftwood. It combines the looks of a planted tank with the practicality of a BB tank.
I don't know why discus are more sensitive than their river mates. But that is not uncommon, slight changes to an environment will kill one species while another will thrive. If you think of all the animal species there are and compare it to the number of species that have made it to the pet trade, it is very small. For one reason or another, their needs can't be met in a household. But you would think that with the huge expanse of the discus habitat, that they would be hardier or at least more adaptable.
I can't help you either with the wild caught hardiness either. But a fish that survives to adulthood swimming with piranhas and still lives through the transition to captivity is probably one tough fish. I too like the look of the wild breeds (I have Alenquers), they will look great in your biotope.

[BlueTurquoise]

This is a great thread.

The poblem is that discus in the wild have such large water volumes that the parasite vs water volume ratio is extreme. If we wanted to mimmick conditions in the wild we would also have to reproduce water conditions very close to those ratios. The point is you will need an Olympic sized pool to create that type of environment! Aquarium kept fish have to deal with water that is high in biological matter including good and bad bacteria and parasites etc. In the wild they don't see that sort of highly dense biological content in the river, so they are not exposed to it as much and that is one factor why aquarium fish are not as "strong" as their wild counterparts.

If we were to try to create an environment that was simmilar to their wild environment we would need to try to reduce the biological content of the water, that means perhaps 50% water change every minute or so! filtration is part of the solution but filters are chock full of bacteria as well. Maybe one day we will find an answer such as UV filters, and other sterilizing/monitoring equipment. Until then the best we can do to raise them as well as possible is to keep their environment as sterile as possible.

See in the wild there may be alot of parasites etc but we talking about millions of gallons of water passing by per day. At home we are talking about 50-100 gal of water per day.

And the point about success rate of captive bread fish over wild fish is probably right, that the wild specimines are very tough, they have to be! they are one of the only survivors of a fry 300 spawn!! Nature makes them tough by getting rid of the weaker ones. That is why we think that aquarium fish are more sensitive becuase in the wild it probably would not have survived this long already.

Anyway this topic of biotope is very intersting. Bare bottom is not a bad interpretation of their biotope when you think about it, considering that the Amazon is on average lets say 20ft deep? so having gravel at the bottom of a 3ft tank means that they are swimming in only 3 ft of water. Also if you have a look at photos of the Tefe river system of the amazon, there is at least 20 to 50 ft in between each stree stump and plant feature, except for the shoreline so to put that into a tank will mean youneed a 20ft wide tank that is 20ft deep! That is the features side of it.

but at home we try to mimmick their water conditions to keep it as pristine as the amazon river system is that is fed with billions of gallons of water every spring from the melting of snow.

It is a toss between features, or what we interpret it to look like, and having their water conditions pristine. I think it would be difficult to get both, not impossible but very difficult.

Anyway I am talking nonsense
Chong