In this instructable, you will learn how to make a small fish tank out of an empty pretzel jar. This didn't cost me anything because I already had the gravel and the air pump, but if you had to buy everything it would cost 30 dollars or less.

NOTE* This project involves live animals. No animals were harmed in the making of this instructable. Also, do not try this with just anything. I chose a pretzel container because it was for food, and therefore shouldn't kill fish. I would have been deeply worried if the fish had died due to the plastic, since we eat food from it.

Step 1: Gather Materials

For this instructable, you will need:

1. empty pretzel jar, or other food grade quality container.
2. small air pump(for circulation)
3. aquarium gravel
4. air tubing, air stone, and air flow valve.
5. something able to cut and poke holes(i used a swiss army knife)
6. thermometer for water temperature
7. access to a sink, and possibly a hose as well.

Step 2: Wash the Pretzel Container

In order for fish to be able to live in this aquarium, we must first wash away all of the salt and chunks of pretzel from inside the container. I did this using an outdoor hose, but you could also use a bathtub, a shower, or a sink. Just make sure you get everything clean, so you don't kill your fish.

Step 3: Prepare the Lid and Air System

For the fish to get sxygen in their tank, I fed an air tube through a hole in the lid into the tank. To do this:

First, cut a hole in the lid, wherever you'd like. It doesn't really matter where. Make sure it is about the width of your tubing, so it will stay in place. Then, attach the air stone to one end of the tubing. Take the opposite end, and feed it through the hole, going out the top.(see second picture.) Pull the tubing through until there is just enough left on the tank side to reach the bottom of the tank.(see first picture) Then, take the end of tubing without the stone on it, and attach it to the air control valve. Plug this into the air pump, and your ready to go.(see last picture for guidance)

If you would like, you can cut any slack you may have out of the tubing, remembering that you want to have enough to reach the pump, wherever you decide to place it.

Step 4: Back to the Sink

Now it is time to start filling up the container with water. This I would do from a sink, and then condition the water after it is in the tank. Once you are about halfway filled, you can add your thermometer, and start adding warm or cold water depending on where you want your final water temperature.

Step 5: Finishing Touches

Now it is time to add the last details. Now, add the gravel in, and any decorations if you want. It is also time to attach the lid, which should already have the air stone facing in the correct direction. If not, just take it out and try again. Now plug in the air pump, and see if it works. If the air stone starts to float, just burry it with some rocks, or buy a cheap suction cup mount to keep it underwater.

This is where the air controller comes in handy. You don't want the flow of water to be too strong, because chances are you will have small fish in the tank who don't like that. However, you do want some air, as well as some current to the water.

Step 6: Wait

As sad as it is, you really can't put fish in right away. You should wait at least a day for the water to get to the right temperature and ph levels, and then it should be able to maintain this for at least another day before you put fish in. Personally, I would wait at lesat a week, to make sure everything is working well and there are no problems.