It wouldn't be difficult to study the effects of acid rain on goldfish, but the goldfish might not like it. There are a lot of government rules for doing research on vertebrate animals, so that we respect their needs and rights. You might try studying the effects of acid rain on plants.

You could water plants in pots with 'rain' that has different levels of acid. You could buy a big bottle of white vinegar, which is an acid. You could dilute the vinegar with water to make different strengths of acid. You could water little plants with the different vinegar solutions that have different strengths of acid. You would want a lot of little plants - maybe you could buy a flat of some sort of ground cover and transplant it into a bunch of little pots. Then you could water them with plain water and with the different vinegar solutions and write down your observations and maybe take pictures of the plants.

Do you know about pH? That is how we measure acid, in pH units, which are like hours for measuring time or inches for measuring distance or grams per liter for measuring concentrations of solution. I see you're in 11th grade, so you probably already know about pH.

Subjecting goldfish to acid constitutes cruelty to animals. Don't do it.

PH affects the stability of molecules and the likelihoods of certain reactions. Changing pH away from what an organism is used to will denature its enzymes and cause them to cease to function, causing physiological hardship and ultimately death.

Aquatic creatures do not have cuticles that protect them from the outside environment the way that terrestrial animals must, and so have no defenses against changing pH.

Changing temperature of the oceans is not as damaging to the inhabitants of the oceans because they can simply move to and from the equator. If global warming continues, the marine ecosystems characteristic of the tropics will expand. For thermodynamic reasons having to do with evaporation and rainfall, the equatorial oceans cannot get any warmer, and the deep oceans cannot get any colder without the complete removal of the Antarctic ice sheet (and the ice sheet is getting bigger, not smaller, due to increased precipitation).

I am not sure how acid rain affects sea life but I am sure there is a lot of material out there that will answer this question. Based on what you find, for your science project I would first suggest you decide which behaviors of the gold fish you would like to test, and how you are going to score them. For example, do you want to see if acid rain affects their appetites, their movement, aggression, death rates, etc? Once you decide which behaviors you would like to test, then I suggest the following. First of all, you want to identify the constituents of acid rain so that you can prepare a synthetic solution of it.

What acids (sulfuric acid, nitric acid, etc.) will be in the water and what pH will the water be? You can research which acids and pH values are most common in acid rainfall to help you with this.

You may want to start with a milder solution at first.For the actual experiment, you will need at least two separate bowls of fish, one to be used as a control where you add normal tap water (simulating rainfall). Then you have to decide how much water you want to pour into the bowl to simulate rainfall. There are a lot of variables you can change, like the volume of water added, whether or not you observe behavioral changes in the short term (the day of and the following days verses the next month). The important thing is, you need to always have a control and you need to probably do the experiment in duplicates or triplicates, to make up for error(some fish may start out sicker than others or be more prone to variable pH than others). If you need more help with the setup I would be happy to assist you.Good luck!