My family has been in the septage business for over 50 years. Septic tanks take care of themselves. Adding yeast or dead groundhogs etc. is like throwing a cup of salt into the ocean to raise the salt level. Problems with septic systems are hydraulic overloading and organic clogging. Septic tanks are like the filters on our vehicles. They are there for maintenance to be pumped routinely, unlike the old cesspolls that only need to be pumped when they are full.
Septic tanks operate at a near full level with a baffle on the inlet pipe to keep inflowing sewage from distrubing and churning up the sewage in the septic tank. There is a baffle on the outlet line about 1" below the inlet line, this baffle keeps the floating scum, grease etc. from flowing into the drain field.
With normal use the septic tank with collect solid material on the bottom and light material on the surface. As the sludge and scum levels increase they decrease the amount of time new inflowing sewage as time to settle out causing the out flowing sewage to the drain field to carry over debris laden sewage. The septic tank can also be called a settling tank as it allows the grease, solid etc to settle out making for cleaner sewage to flow to the drain field. It is an antiarobic system which doesn't require oxygen. The use of cold water detergents that were popular a while ago contiained phosphorus to create the heat in the washing machine when mixed with water. It is our experiance that the phosphorus re-solidifies in the septic tank casusing a quicker build up of scum on the septic tank surface. To know when a tank needs to be pumped, a person can open the lid using safe practices on large openings,and check the thickness of the scum level on the surface of the tank. It should not be more than 5-8 inches thick. It is difficult to know how deep the sludge is on the bottom of the tank but if the scum level is little to none after 3-5 years it would be wise to pump it to find how your family use affects the system. If you have a garbage disposal, you should have your tank pumped more often because of the extra solids put into the system. The average pumping should be 2-3 years. Bragging that you haven't pumped your septic tank for many years is like bragging you haven't changed the oil filter in you tractor for years. If debris is carried over to your drain field the grease and detergent seals the pores in the soil preventing the water from being absorbed. This is called organic clogging. If your drain field becomes over loaded with sewage this would be hydraulic overloading. Organic clogging cannot be fixed, new drain field. Hydraulic overloading could be from a dripping spigot or running toilet, if you have to juggle the toilet flush handle, fix it, a running toilet can add an additional 28,000 gallons of water to a 1,500 gallon septic system in a year, thats a lot to expect the soil in the drain field to disipate. I hope this helps, relax flush you paper but not sanitary items, stop leaks and drips. Don't add anything extra and find a good sewage management company that has certification. I hope your find this helpful.