at some point, nearly every aquarist dreams about a tiny representation of a piece of the earth that is completely closed off from all environmental input. you know what i mean, the ecosphere type setups that are completely sealed, only letting light in and very rarely, if ever, air. it is a beautiful idea, it is essentially creating a microcosm, a single window into the entire process that take place on earth. you know, the process we passingly refer to as ecology. it is a dream that has been with aquarists and naturalists for years. some say it has never been done, many say it cannot be done.
that last assumption is complete BS. the one prior only partially so.
before i explain that it is not only possible, but indeed very simple, to create a self sustaining closed system, let me dispell any delusions of grandure that may be building up in anyones head...
you will never be able to keep a healthy goldfish
in a closed ten gallon aquarium.
i have spent the last fifteen years or so getting closer and closer to that holy grail of aquariums, and i have learned a LOT of lessons along the way. here are a few things i have learned and come to realize that may help someone else who chooses to pursue this "unsolved equation".
first and formost is the size and complexity of the animals and plants that are to be kept in a sealed system. lets say we take a small fish, the dwarf livebearer (heterandria formosa), and a simple plant, java moss, and put them together in ten gallon and seal the lid. we will add light and keep the temperature stable, but that is about it. the rest is up to the fish and the plant.
ok, so we have a fish that will live a lonely life in ten gallon tank. that would be kind of like giving you about half an acre of living space. in fact, you would have about half an acre of lawn, about 60 feet of space above your head, and lightly filtered sunlight. now, lets place ourselves into the fins of our new sealed systems inhabitant. for a little while, things are ok, kinda lonely, but hey, at least you have some room to move around. after a little while, you start to get hungry. this is a problem... there really isnt much to eat, but if you look really hard, you can usually find some tiny bits of dying plant matter to eat, as well as the ocasional tiny copepod here and there. its a good thing you have a tough stomache, otherwise you might be in trouble. so food is taken care of, for now. as the first day drags on, things seem not so bad, the light is hitting the plants and the plants are quickly using up all that annoying CO2 in the water with you, giving you plenty of nice fresh oxygen to breath. along with the CO2, the plants are also soaking up all the nasty stuff that you release with your number ones and number twos. the food sucks, but hey, you cant really complain too much.
later on in the day, god decides to turn off the lights. you expected this, nothing new. after a little while however, that nice little oxygen bar you had sitting on top of that nasty tasting plant starts to get a little stuffy. you see, plants only exchange oxygen for carbon dioxide while the lights are on. without the photo in photosynthesis, plants have to use oxygen from the water and expell excess CO2, which they can no longer use. as the new king of your own little ecosystem, this translates into a really lousy day. the CO2 levels are rising, the O2 levels are dropping, and that friendly plant which is now using oxygen faster than you are, doesnt seem so friendly anymore. not only that, the water is getting sharp! by the end of the night, there is so much CO2 in the water that the PH has dropped to dangerous levels and you are really starting to feel the heat. the acid water has left your gills inflamed and you are starting to feel like you are literally suffocating. it wont be long before you slip into unconsiousness...
about this time god(the "benevolent" owner of your new little world) decides to be merciful to you again and turns the light on. slowly, you come out of your oxygen deprivation induced stupor and start to look around. it seems your not the only one who suffered last night. that plant you were hanging out at yesterday has several leaves that look soft and pale, with tiny holes in them. it obviously had a lot of trouble last night, as several patches of it have begun to die back. that means more lousy tasting food for you, which is great and all, except that you still feel sick from last night and really have ZERO appetite. after a while though, the parts of the plant that are still alive soak up a lot of the CO2 and things start to get a little more tolerable. the water never quite returns to that freshness that it had on that first day, but eventually you feel good enough to get hungry. this time, there is plenty of dead and half dead plant for you to eat. with nothing else to eat, you gobble it down. by this point you are relatively comfortable again. what is left of the dying plant is starting to rot, so the place is getting a bit stinky, but you arent hungry and at least you dont feel like you are suffocating anymore.
then someone turns off the lights again. you begin to go through the same hell you went through last night, only this time its worse. the plant is sucking up oxygen again, but its not the plant that is bothering you, its the combination of the plant and the bacteria that are eating the dead plant parts that are sending you for a loop this time. if it were just the plant, it wouldnt be so bad. the ph and CO2/O2 swings would be less severe tonight than they were last night, as there is less plant to compete with you now. add that pesky bacteria culture though, and now you have a recipe for disaster. by the time the lights come back on you are barely alive, sitting at the bottom of your tank gasping for air in an oxygen deprived coma.
eventually you wake up feeling absolutely miserable. during the night, your body shut down all non-essential processes. that means you took a nice massive number two while you were out of it. that really sucks, because you werent even done digesting that food. your situation now is looking pretty bleak. the water never really returns to the state it was on that first day as the bacteria are using up any extra oxygen just as fast as the remainder of the plant can produce. on top of that, you are slowly suffocating, you are weak from not really being able to even eat the nasty nutrient deplete food you ate yesterday, and you have have digested strings of plant matter hanging out your back end. you try moving around to several places in the tank, looking for better water. its useless, it all sucks. unfortunately, the god of your world sees you swimming around slowly and thinks that you are doing fine. to him, you must be healthy, so he keeps up what is obviously working.
later, he never fully understands why you were dead the next morning.
so, now everyone should be clear on why you would never be able to simply seal some fish up and have any positive results. now that that is clear, on to the second half of this incredibly long winded post...
the first mistake i see in almost every system that i have seen that supposedly recreates mother earth is that the lights go off at night. it is a rediculous notion that because we have a night, no light should reach a closed system for half of every day. let me dispell this myth: a closed system should ALWAYS have a light on it. this may not make sense at first, but think about it, when does the sun not shine on the earth? at night? nope, just shines on the other side. we are still connected to the side the sun shines on by the biosphere. if you were to completely replicate nature, you would need two tanks that can circulate water and maybe air between them and only light one at a time. you would never under any circumstances turn off both lights. well, you certainly could if you wanted too, but it would be nothing like earth, which is always bathed in sunlight.
the second mistake i often see is the assumption that a fish, provided with a plant that it can eat, will be able to live off of that plant. from time to time i still see bettas being sold with a bamboo shoot in its bowl with the idea that the betta
will live happily off of the roots of the plant. its the same kind of mistake that uneducated pet owners make when they assume that feeding their turtles and bearded dragons lots and lots of lettuce will keep them healthy. if you were to replicate nature, you would have to create a system that can grow enough food to meet ALL of the nutritional requirements of its highest level organisms as well as maintain good gas and nitrogen levels. you would also have to find a way to safeguard your food populations from extinction. this means that at least some of each species would have to be protected from the animals that eat them so that they can produce a constant supply of food. without this, you will never be able to reach or maintain a balanced ecosystem.
the third mistake i see is the misconceptions about size. im talking about the living-thing-to-environmental-space-ratio(aint that a mouth full). to put the good ol reference(nature) into perspective, think about how big living things get on earth. then imagine the size of earth itself. put the two next to each other and you start to get my point. if you were to put even a tiny dwarf livebearer into a ten gallon tank it would be like expecting a creature half the size of the moon to live on earth. if you have ever tried sealing a container and saw what lived after a year, you would have noticed that the things that remain generaly need a microscope to examin. life does not die out completely as long as energy can go into the system(light), but nothing big lives for long.
this is what i meant by a sealed self sustaining closed system being quite simple to set up. the question is not about whether it is possible or not, but rather about the definition of success. personally, i find microscopic life to be just as fascinating as macroscopic. a closed system can certainly sustain microscopic life for seemingly indefinite periods of time, therefore a balanced closed system can
be created, at least by definition. well, sort of... a truely closed system that actually lives would break the third law of thermodynamics... but thats beside the point.
now, after having said all this, i still believe that it is possible to create a sealed system that can support fish. it would just have to be very complex, with ways to circulate resources around it while maintaining a balance of the resources and life within it. i for one am going to continue to find ways of creating this system. my goal is to be able to create a system that can live for 20 or more years without any resource input except for light and heat energy. i believe i am a lot closer than most, and i believe it is possible, even though i am highly skeptical of even myself.
anyway, i hope you all enjoyed the long read and maybe walk away from it either inspired or enlightened. my hope is that someday someone will create what i view as the holy grail of all aquariums.
who knows, maybe it will even be you?