what is the best soil/ soil mixture for seedlings?

would this be okay?
Supersoil - Products - Supersoil Potting Soil

and how big should the container be?

Seedlings need a soil that is lightweigt so the roots can grow freely. A commonly used mix consists of sphagnum peat moss, peralite, & vermiculite. Container can be numerous sizes - kinda depends on how many times you want to transplant & many other factors.

rockwoll cubes are good, or some nice MIXED up soil(perilite, moss, soil, etc). If you go soil, which is just as good as rockwoll, just get a \"party cup\" sized pot. And remember to beware of what is in your soil.

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what ratios of the sphagnum peat moss, peralite, & vermiculite?

Ive seen some real nice pre-mixes you can get... But its pretty hard to go wrong when making your own mix... equal amount of each element mixed up should do great with majority soil

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make your own mix of soil,it should have an organic smell to it that has a airy texture and that denses up when wet,u should use the same soil for the whole grow as well as one pot if possible,a 1-3 gal pot will do just nicely

so is that supersoil in my first post okay if it is lightened with perlite?

Well... It does have this----- \"no fertilizing is required for up to 90 days after planting.\" ------ Which wouldn\'t help unless you are vegging for 3 months. In reality you would be just fine with it, but it could be better.

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so it shouldnt be harmful then?