i have several mango from seed.

i normally sprout them in a 1.5 qt container, and move them to a 1 gallon within a couple of weeks, or, until they are about 8 inches tall.

My rule of thumb is to have the container as tall as the height of the plant. (at least while they are small)

Normally, with larger trees, you can go much higher with the plant, double, or even triple...

But, i dont want the tap root touching the bottom of the container, especially with a mango, if i am going to plant it in the ground one day.

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as far as germination...

i did a test, with 1) paper towel - 2) paper towel and fulvic acid - 3) paper towel and worm castings...

the worm castings produced much stronger and larger seedlings.

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soil...

personally, i dont like coir (or peat)

but, i am not like most growers. i like live soil, more organics, less chemicals. i also like sand and lava rock (just a few)... the lava rock has small holes that retain water... coarse sand has great drainage and slowly breaks down releasing minerals.

nothing beats quality sifted compost... bark fines are good also.

i use about %15 local soil for the live biology. my soil is a fine sand with some organic matter.

and i use about %10 or %15 worm castings.

Like i said, a lot of people will disagree with me on this, especially on the local soil.... and FINE sand 'can' get you in trouble, but it works for me. (dont use much and mix well),

%25 bark fines // %25 sifted compost // %25 coarse sand // %25 mix of - lava rock, worm castings, local soil and/or perlite - to taste :)

Wow! That's an interesting mix you got there! Gonna be tough finding that in stores. That being said I do have some organic worm castings!!

Would you be able to elaborate on the third method "paper towel and worm castings"? Is it just the same - wrap mango seed in a warm damp paper towel and have some worm casting around it inside the bag?

yep... just add castings to the bag, so the roots can touch it if you can... the moisture should carry the nutrients though even if its not touching the roots directly... i would not use chlorinated water though... let a 1/4 glass of water on the counter for 2-3 hours and the chlorine should evaporate.

bark fines, sand and lava rock are all pretty easy to come by at a nursery, or even home despot.

Greenman pretty much summed it up. I would add..NEVER use too much peaty potting soils. Pro growers dont use that because is goes sour so easy. Use any non peaty mix (or dilute what you have) and just water with a good balanced liquid fertilizer or maybe Osmocote to give the growing seedling a shot.