Cyano bacteria is not necessarily an indicator of cycling, even a three year old tank can experience
Cyano from time to time. It is often a sign that there are excess nutrients in the tank that they can feed off of. Reducing their food source is the best way to control them. What are you feeding your tanks?
As far as a
skimmer, you are going to have a hard time finding a
skimmer that will work on such small tanks. Regular water changes with good salt and
RO/DI water will work just as well, maybe even better.
Siphoning can be done with either a commercially available kit, or by simply buying some small vinyl tubing. Larger tubing will drain water faster and in tanks your size that may create a problem, so keep it on small size. I would try something slightly larger than airline tubing to start with.
