hogan, it depends on the wood you collect... i recently went and collected some dry dead oak and some bits from a boggy area, they have started to sink fine, and im going to use them about a 2 weeks after collecting. as for types of wood oak is good, and any none sappy hard wood, iv used apple in my shrimp tank before (freshly cut) without a problem, it did have a little white stuff on to start, but that syphoned off and never came back. but id say oaks your best and safest bet