Bio-tank Self sustaining life.

[Reignbow]

Hello, I am new to the community and have only kept simple fish in simple tanks. With the help of a friend of mine who who took some biology in university, we would like to start a self sustaining environment! Neither of us know where to start, but our first goal is to have a self cleaning sustaining system that just requires adding water to replace what has evaporated. We are also toying with closing the tank to try a closed system.
We actually decided to do this during a small debate with some friends of ours who bet us $1000 that it was not possible.

The rules we have been given are as follows:

1) no unnatural filtration or aeration of the water or soil
2) no water changes
3) no feeding of critters by adding non sustaining food
4) must self sustain at least 2 fish

We have a 30 gallon fish tank, and would like to start with plant life snails and microbes. We will probably keep it in that state for 6 months or longer and we'd like to create a low light system for slow growth.

We know that at least this is possible, we have heard of others being able to keep a system like this for years, just no details as to how.

At some point we will add small very population of fish and have them replicate or sustain them selves or at least sustain them selves through their own life cycle with out reproducing, and re stock as needed.

With your help, we are hoping to create this biology experiment, document it with video and post it on youtube.

We are allowed to add plant nutrients, and add collected rain water to replace evaporation.

Do you think this can be done? Or do you think I am short $1000 bucks?

If anything I would like to at least try it and see how far we can go!
opcorn:

Looking forward to hearing some replies!

Reign.

 

[MoonstruckMuse]

Honestly, unless you choose some REALLY small fish (look up some nanofish, the kind people keep in tiny tanks), fish usually produce too much waste... and need too much food. Vertebrates just use a ton of energy like that.
I'm inclined to think that you could probably get this to work though, with a lot of manipulation. You might want to look into Diane Walstad, who wrote some great stuff on natural aquaria.

There's a couple different ways to approach this, but regardless, you must keep in mind this - very little energy moves UP through the food web. They always like to quote that the grazer only gets 10% of the energy supplied to the grazed, and the hunter only 10% of that, etc. In that sense, you probably should be using higher lighting, because you want to support a strong plant base. In the wild, it's pretty uncommon to have a low-light, non-aerated area that can support fish - fish need oxygen a lot more than inverts. Oxygen is going to come from a few places - the air (labyrinth fish like the betta might be your friend here), plants (which would need higher lighting if producing large quantities of O2), or from mixing (rivers, waves, etc). Without oxygen, and WITH waste, you'll end up with nasty anaerobic bacteria that will quickly kill most animals with their byproducts (most famously, hydrogen sulfide).

So basically, you're going to want lots of plants (med light) with a rich substrate (mineralized soil) if you want good support at the base of the food web. Zooplankton and phytoplankton populations are actually quite hard to manage, simply because they boom and bust so frequently. You'll want animals that DO NOT breed, because otherwise they'll too rapidly use up your resources. If you could find snails or maybe blackworms that would like to eat detritus, that would help... but only if your plants have decomposing parts, enough to feed them. Otherwise, a snail that EATS plants might be better. The organisms (infusoria) that are fueled by the processing that the snail does to the food can further break down food, so that none is really "wasted" to organisms that aren't your fish. If you raised small, slow-growing fry, you could probably keep them sustainable under these conditions if there were only 2.

 

[ExPeNsIvE HoBbY]

This is a very interesting experiment.
I would say it seems like it would need to be a fairly large volume of water, and possibly small fish that eat plant matter, with TONS of plants in it...

Also lower water temps might help with the metabolism of the fish to slow, to a rate that they could be sustained by a smaller amount of food than we feed our fish normally...

I have a 55gal tank that gets neglected 10 times more than any other tank, which houses 4 convict cichlid(2 mated pairs) and they only receive small portions of food, but they seem to be thriving.

The tank is quite dirty aesthetically, but mainly because of algae growth etc, but it tests with good quality water params, and it almost never gets waterchanges, and only has 2 air driven sponge filters that haven't been cleaned in about 8 months. The fry eat stuff off the filters, and the parents eat what I feed them, which is VERY little...

It's crazy how sometimes the neglected tanks do so well...

 

[Margit]

Hi,

interesting experiment. However, 30 gallons seems a bit small.

If I had to try, I would go for cyperus alternifolia and floating plants. Until recently (I moved), I had a small lily pond. I would guess it was between 300 to 400 litres. The cyperus kept the water clear and the huge roots of Nile cabbage as well as some algae growth on the walls of the pond and decomposing vegetation provided food for 2 tilapias and hundreds of guppies (I had originally stocked the pond with the tilapia and 10 guppies). Of course, there were also plenty of mosquito larvae and whatever other critters wound up in the pond. I never fed the fish. I only topped off evaporated water. There was no filtration or aeration.

I don't know where you live (probably easier accomplished in the tropics). But try to provide natural sunlight and leave the top open to attract insects. I would go for a pair of wild guppies...

 

[Rbishop]

I think you will be out $1000. If you are truly just going to use rain water for evaporation issues, sooner or later you will lose the buffers needed to keep the pH in an acceptable range for aquatic life and the tank will crash.

 

[Fishfriend1]

If your really gonna try this, go with 90+ to lengthen the time your tank can last without any major incidents occurring. Personally, I think this is gonna cost you more then your gonna make from winning that bet.

Good lights, tons of plants, some snails, some fish.

My 30gal has a set of truly ancient lights on it, but they work fine for me. You'll want T5s (or whatever there called...). You'll want to get tons of smaller plants, with a number of larger ones as well. Between the small ones(for food) and the big ones(for Oxygen) your gonna have a very green tank. Fish wise... maybe a few neon tetras(5-7) or something around that size. Maybe some female guppies(3-6). Or a betta(just 1). If your not going to have mechanical filtration, put a HOB on for water circulation and aeration, you can say it represents a stream or other water source. If your gonna use rain water to top off the tank (i do not recommend this) you will need to keep close tabs on the params, make sure the rain water doesn't have anything really bad in it.

I am a true believer that fish are far hardier then we give them credit, so as long as the tank stays stable and starts off with the best conditions as possible the fish should be able to adapt to the slowly changing water chemistry. Mine do fine, despite being tropical fish in a (currently) unheated tank that never gets above 60*F or so. They can also adapt to various Ph levels and even nitrate/nitrite levels.

Do you know what the ammonia cycle is? The ammonia cycle is what we fishkeepers call the cycle that gets rid of ammonia and nitrates and keeps nitrites low. Ammonia is produced by fish poo and other decaying stuff (uneaten food, dead fish, dead plant matter, ext...). Beneficial Bacteria (BB) develop with time, they take out the ammonia and turn it into nitrAtes. Then more BB form and turn the NitrAtes into NitrItes. And finally, more BB form that eat NitrItes. They live in the filter, on rocks, in the substrate (recommend sand for planted tank), as well as in the water column. You want to keep these happy, so no major changes in water chemistry. If they die, your tank will suffer from "new tank syndrome"(tank re-cycles itself with time) which will probably kill of most of your fish.

The fish I recommend for you are female guppies. Not the colorful ones, the ones you see in feeder tanks that are dull brown in color (pics at end of this, first 2). Guppies are hardy fish, and can survive in most conditions. If you get males... don't, they will breed and crash your tank almost immediately, i can garentee that your tank won't last if you get males and females. Guppies like to school, so 3-6 would be a good number. They get to be between 1-3 inches long, but will do fine in a 30gal tank. NOTE: The females have a rounded fin at the base of the tail, mature males have a pointier one, called Gonda-something.

Test the water! Every day or so. Get a basic water test kit (ammonia, nitrAtes, NitrItes, Ph, High Range Ph) from your LFS and use it as the directions state.

Plants and Lighting. Can't help you with the lights, I've never really bothered to get specific with them. I have heard of T5s, but those may be SW only, IDK for sure. Plants: Java moss, I've heard tons about it, know nothing. Swords, I have 2 in my tank, they do great. Duckweed, a great foodsource for the guppies, they will enjoy it. I know mine does. I also have a mossball, which most fish will eat. First time I got one, it was demolished, but this one had done really well, its about the size of a golf ball, and has some nice trailers handing off it. Algae, if your not going to do WCs then you will have to deal with the algae growing on everything, even slow growing plants. Your tank will not look pretty except from the top.

Filtration, you will want lots of plants, a 1-2 inch sand bed (sand substrate = more BB, i think). Plants will help take out CO2 and put in O2. Also, get a powerhead or Hang On Back (HOB) filter, for circulation. I have on my 30gal a single Penguin 350 (for mx 70 gal tanks) and it does a great job. But yours will only be there for circulation, so you will want to take out the filter media (cartridges that come with filter).

Water Parameters (Water Params)
NitrAte= 0 ppm is what you want.
Ph= 7.5 is best. Do not go below 6.5 or so, probably not above 8.5 or so.
NitrIte= 20-40ppm is where that should be in a stable tank.
Ammonia= 0 ppm is what you want in a stable tank.

If I missed anything, someone else can cover it, but I think I covered everything.

Good Luck with your experiment!

 

[thebrandon]

This is going to be very hard, even near impossible to do for a long period of time. It can be done with snails for sure. I have done that. Not on purpose but just because of how great bladder snails are at surviving what ever you put them in.

 

[vanillaXtiffy]

Animal cruelty, IMO. But whatever floats your boat I guess.

 

[Margit]

Animal cruelty, IMO. But whatever floats your boat I guess.

Here's a good account of an experiment with a self-sustaining system: http://www.tuncalik.com/2009/09/biotope-in-my-study/

However, it was a sizable tank with a tiny number of tiny fish...

 

[thebrandon]

You might be able to do it with a live food in there like blackworms maybe? I'm sure they would populate the tank if there were only two, small predators in there.