Vinegar Eels are a great first food for free swimming betta fry. They don’t sink like microworms, banana worms or walter worms; tend to swim near the water surface and also live longer. They also keep the fry off the bottom of the aquarium which makes siphoning out waste easier. Harvesting them is a bit of a pain. Since they live in half apple cider vinegar, half water with some apple chunks (or sugar)… they must either be forced into fresh water or filtered through a very find sieve or coffee filter.
Pour some of the culture into a clear bottle with a neck (to just below the neck). Shove filter floss inside the next down to just where the vinegar starts and pour fresh water above the cotton plug. A string or wire should be tied to the filter floss to get it back out. Leave over night and the vinegar eels will, in theory, climb up into the fresh water to get oxygen. This method never really worked for me.
Pour some through a coffee filter and feed. This works but the smallest worms are sometimes missed.
Wait… there is a third method? Yes, if you are lucky. My cultures are exhibiting a peculiar behavior. The vinegar eels climb out of the culture like microworms would do. The original culture had apple chunks as food but the second two (started from the original) were just fed a bit of sugar. All I have to do with mine is swipe some off the glass, with a q-tip and swish in a little cup of water (When the eels climb they form clumps so it’s important to detangle them before feeding). Then I just squirt some into the betta fry tank with an eye dropper or syringe (you can find a syringe with a bit of tubing attached often times in the baby isle to give medicine or for handfeeding birds without a needle — which is what I have). Start with a small amount until you understand how many your fry need… The eels will die eventually if you put too many in there.
The way I have my vinegar eels cultured might make a difference. They are in half gallon jars about 3/4 full with a coffee filter rubber banded over the top. Searching online yields no specific information on what causes the vinegar eels to climb.