Ok i have a just under 10 gallon tank 6.8 g or 26 liters and plotting to have plants like a carpet ,some sort of grass or sow ,i seen A Diy co2 system using yeast in a soda bottle type configation and was wondering what are the effects if i use in on my small tank..

I have had my fish tank for 2 years now and it has only ever needed fully cleaning out once a month. Why all of a sudden is it going green after only 1-2 weeks of being cleaned out? The green that is appearing in the tank is not the normal dark green algae that naturally occurs but a more mid-green colour. Nothing has changed with regards to the tank apart from the addition of a small crab but I can not see him being the problem! Any thoughts please let me know.