沙層內會有氣泡產生請問這正常嗎
Yes. This means your sand bed is working.
且有一小面積的沙子有紅色泥狀藻產生該如何消除呢
For two months, your tank is still going through algae cycling, what you have is cynobacteria. DO NOT ATTEMPT TO ADD ANY MEDICATIONS TO TRY TO RESOLVE THIS but rather let nature take its course. Heavy skimming also helps in this situation. It is normal algae cycling, OK???