white stuff in my aquarium..and alkalinity problem?

The white stuff is probably slime mold, just wipe it off or gravel vac it out, it just lives off the bacteria in your tank, very common during cycling. Exactly how alkaline is the tank pH? Did you test the tap water pH? Treated city water is usually quite alkaline, otherwise the alkalinity could be caused by ammonia, try using a cycling product, like sera nitrivec to help your tank along. Adding fish food also helps by increasing the level of ammonia, which encourages ammonia eating bacteria. You can get driftwood from most fish shops, or you can collect your own.

My procedure is to pour boiling water over the wood and leave to soak over night, (boil in pot if small enough). Then soak in one tenth bleach solution overnight. After that I do the boiling water thing again for a few days to make sure all the bleach is gone and nothing else grows.You will probably need to weigh down the wood and soak it for a week to get it to sink. It may never sink, mine didn't so I used a combination of natural rocks and bathroom silicon to stop it floating. Remember, the pieces of wood have to be really dry and preferably white looking, so that all the tannins and sap are gone. It might seem time consumng, but the wood you buy in the shops isn't guaranteed to sink either. The best places to collect wood are river or creek banks and beaches.

Even if the pH is high because of ammonia, many fish prefer droftwood in the water as it releases humic acid, this lowers the pH and generally creates a more natural environment. This is mostly true for south american and asian fish.