What if the top of the sand in some places is crispy. When I touch it I can break through and then it's soft under neath. I heard it was because the tank didn't have enough flow. I have fixed the flow issue, but have noticed the sand is still crusty in places. It seems like it may be crusty up under the rocks too, but I can't reach those areas to check. I just don't know if I need to remove sand or just take some of the top off during W/C, or if there is another option. If I have a YWG will he still be able to stay in the tank?