Looks like earthworm egg.

looks like fertlizer to me as well.
from my experience, cinnamon does very little to help control gnats.. if you see them then chances are there are eggs already buried in the soil, the cinnamon has no effect on larvae, it might help with keeping the ones that are alive away, but again, it won't address the eggs already in the soil.

neem oil works great for killing the larvae in the soil. you add about 2 tbsp per gallon of water and drench the soil with it. another option it to let the soil dry out for a bit. the larvae are usually within the first 1-4 inches of the soil and letting it dry out will kill the larvae.

i'd advice addressing the gnats problem as soon as possible because it will get out of control very quickly.. the gnats/larvae feed off bacteria/fungus in the soil and when their food source runs out they will begin eating the roots hairs of the plants.

I vote fertilizer also

It seems like miraclegro and fungus gnats go hand in hand. Fungus gnat larvae feed on the organic matter that our soilless mixes are made of! Add excess moisture to these mixes and you create a perfect environment for the pests. They will feed on tender root tips right along with the peat moss and other tiny bits in the potting medium.

That the larvae are feeding on fungi and bacteria within the medium is not correct....it's the actual components of the mix that they ingest. Miraclegro is a fine textured peat based product; it seems to stay excessively moist for long periods of time.

Providing our plants with a coarse textured, fast draining mix can go a long way in preventing a habitat for these pesky insects. Careful attention to proper watering is also important, but a really coarse mix is almost impossible to over water.

Larvacides, such as Gnatrol or mosquito dunks, are excellent means of control but focusing on fungus or other organisms in the medium is not the way to go.

Fungus gnats can be a problem with any potting mix IF you over-water and keep the soil overly wet. But I agree that cinnamon is of no benefit to controlling them. Quit the excessive watering and they die off all on their own. Or use the Bt prep found in the Mosquito Dunks.

Dave

PS: just opened a new bag of MG Potting MIx - all kinds of little yellow balls of fertilizer in it. They tend to float up to the surface when the soil is too wet.

Message from my neighbor Who is a horticulturist: Actually the yellow opaque pellets filled with liquid are slow release fertilizer. The white pellets are perlite and are an expanded mineral meant to create porosity in the growing media.

If you notice gnats with your indoor plants go the the store and get neem based products and do a soil drench with double the label rate. Also be sure to let the soil dry out between watering, that will help with gnat prevention.

What everyone else said, plus...I have good luck with yellow whitefly sticky trap strips next to the pots. Actually they work well on window sills. That and less watering hold them off and no need for chemicals (for me).