algae in my aquarium

Question
i put some rock that i found at the dollar store in my 20 gallon freshwater tank. and all of a sudden my live plant and all my rocks look dirty with algae. even the ones i bought from the fish store. i like the rocks i bought at the dollar store not cause of price but because there the big creek looking stones and it looks more natural then the little colored ones i see at the fish store. i read on ask jeeves that because the rocks are not aqaurium safe thats the problem. well how can i make them safe???? the rocks the pet store used has to be made safe somehow. do you know. i read some guy on jeeves sayn that he would clean all his fish decor that he found in a little bleach then let it sit in the clorine remover for aquariums. what do i do. i has just changed from a 10 gallon to 20. the rocks were not bad in the 10 gallon until i went and bought more to fit the 20 gallon. Help?? Thanks

Answer
Hi Lynda;

I think the algae is probably a coincidence and not related to the rocks. It must really like the conditions of your 20 gallon better than it liked the conditions in your 10 gallon. It's usually the lighting. If your smaller tank has incandescent and your 20 gallon has fluorescent it's even more likely. Fluorescent tends to be brighter and sometimes grows algae more.

It is better to only buy "aquarium safe" rocks and decorations for your fish tank. These rocks really aren't "made safe" before they go to the fish store. Natural rocks can be safe as long as you know they aren't from polluted water or have absorbed toxins. The fish store rocks are simply from safe sources like that and are not exposed to or treated with any chemicals before they get to the fish store. I have seen rocks in the local dollar store or walmart too but I don't use them in my fish tanks. Who knows what other products they were shipped to that store with? Could they have been in the same packing boxes or on a shelf below some pesticides, hair dye, cleaning solutions or other toxins at some point? Or, could they have been dropped on the floor and come into contact with floor cleaner? That stuff may never be completely removed as it absorbs into the rock. Since the rocks are meant to be used in crafts and garden projects no one would think anything of it. This is not to say it can't happen at a fish store too and they are packed with a "flea dip" bottle next to them or something. It's simply that the chances are greatly reduced in fish stores because they were known to be intended for a fish tank eventually. Personally I just feel safer with those than others.

At Your Service;
Chris Robbins