Since nobody has answered your question, I will take a stab at it.

I don't have personal experience using VC as a growing medium. My understanding is that you want to mix 1 part VC with 4 parts potting soil.

Thank you. I have definitely been using too much VC!

With only a year of vermicomposting under me' belt I will give you my experience from last winter/early Spring. I started seeds in soil from my garden beds ( each bed soil was kept separate and labeled ), seed starting mix, and straight VC. The straight VC did not do well...at all. Surprise, the seed starting mix worked best. The soils did OK...I guess that is why there is seed starting mix. I did add VC to all my seeds I sowed into the ground, and also all my transplants.

Kath, a bit more information would be helpful. What does your media consist of, and is it mainly worm castings with which you are attempting to germinate seed. The worm castings may be hard to define, but is it a dark black color? Worm castings are probably too nutrient rich for seed starting, but great for potting mix formulas.

My bins are cardboard and newspaper for bedding, and I pocket feed food scraps to the worms. It is dark black. I first tried 100% VC and it was a complete failure. Then 75% VC with square foot garden soil - equal parts compost, vermiculite and peat moss. Some sprouted and died out shortly after. Then 50% VC and sfg soil-more sprouts but died out again. I think you're right about it being too nutrient rich. I am currently patiently waiting for 25% VC and sfg radish seeds to sprout. Does checking every hour count as patient? :) I guess if this doesn't work I will buy seed starting mix. :(

One more note; I had heard that they use 50% VC and 50% coconut coir at growing power. Has anyone used that? Thanks.
Kath

I use about 20% VC to 80% coco coir after reading research from Cornell

The mention of coco coir led me to research the topic more.

I first posted about using the outside of coconuts inside of my worm bin because I had gone to a vegie (vegetarian vegan raw foods) potluck supper and the mention of health benefits of coconut water inside baby coconuts was interesting enough to encourage me to get a few baby coconuts. They differ from mature coconuts by having water and maybe a pudding like start to coconut meat in them. As a vermicomposter kitchen scraps are where it is at so I put the shells with the inch thick fiber coating on them into the vermi bin. After a few times through I was able to peel off some nice material from the shells. The worms seem to like it. Adult coconuts in the store do not have this material on them. Baby coconuts in the store are white with pointed tips wrapped in plastic.

From my online search I see that in addtion to the strong fiber that is made into ropes a material called coco coir may be the material between the strong sturdy fibers covering the coconut. This powder may be a scrap material after the valuable fibers are harvested. This material has some magical properties. If rinsed of all salt the material seems many times better than peat.

The forums that seem to have the most technical, scientific explinations and educational conversations for what is happening with the surface area, oxygen, electrons, and nutrients in the soil are not growing radishes.

But now I want to add some of this coco coir, the dust inbetween the fibers of the coconut to my bin because if I add biochar I think my worms will think they have died and gone to heaven.

It is all about providing the wee beasties surface area with a film of moisture and oxygen and maybe some mycelium to help the goodies travel quickly to where they are most needed.

Kath, another thought about using VC for seed starting. How wet is the VC. If your seed starting material is saturated, the seedlings can not get air to the roots, and will die rather quickly. Air is just as important to plant roots as water. Too much water and plants will expend more energy into growing roots that leaves, and when soil goes anaerobic from an over abundance of water the fine new roots don't have a chance.

Many people do not like peat pots for starting seedlings, but I have worked with peat moss for years as medium for my worm beds, and peat pots are very similar. Once you get use to using them, peat pots will tell you when you need more water, and they tend to dry out faster than plastic. it may take some time to decipher when to add water, and when to back off regardless of what type of container you use to start your seeds in, but over time you will learn to tell how much and when to water.

Depends on the study. I've seen anywhere from 5%-25% VC tested to be optimal depending on growing conditions and species of plant.
10-15% seems to be a good compromise.

Personally, I use 13.4729%.

Naaa, just kidding, I just grab a handful and mix it with potting soil. ;)