rocks.....

can i use rocks from my backyard in my tank?

yes you can put any rock in tank. wash it off very good before

wrong.

whats right??

You need to PH test it before you use it. wash it well and put it in a bucket with tap water. Put tap water in a 2nd bucket. Do PH tests several times on both buckets for a few days. If your readings are the same you should be ok using the rock in question.
There's also a vinegar test.... Not too sure how thats done though

also, the color of rocks are hints to their composition. certian rocks (white colored rocks)may contain a lot of calcium (lime), which is great for certain fish/setups, but it may be counter productive with other fish/plants/setups.
red typically means that is has a lot of oxidized iron. iron is needed for some rooted plants, but too much iron can cause little black dots on leaves.
greens and blues are clues that a rock has copper in it.
greys and blacks could be granite or iron or quartz. to know whether it is iron, quartz, or granite you would need to consider particle size and shape. i.e. a round rock is a clue that it has been smoothed out by running water. rock composed of iron found in streams and rivers would tend to be red not black or grey.

I know that certain compositions have different impacts on different aqauriums, i would like to post a comprehensive list, but I will have to do some more research first. I have sent a message to a friend of mine. I'll post when have more info.

mason the red is usually an indication of iron.

i didnt know that