FishBait

We use quite a few onga pumps at work. they pump with good preasure and head. They are designed for swimming pools but run a lot of our systems. We use a few pressure sandfilters from them too.

As carol said the first guess is Planaria which should be easy enough to confirm. If they are Planaria try adding a gourami ,i have found the dwarfs great. The Gourami love to chow down on the Planaria and other crawlies. you should find in a week or so the plague is amost gone. Most outbreaks can be traced to collected live foods, new plant etc but some times can seem to come from nowhere. They don't need a mate to start multiplying and can divide like a anemone. Generally they are no problem to the fish, eat left over food but can kill and eat eggs. Good luck but don't stress

Well Done and good luck. I have had a better success rate by leaving a small night light on. It gives the adults a better chance to defend the brood, in the pitch dark they can have trouble seeing any threat that sneaks in under the cover of darkness. a kids bedroom nightlight is great.

What sort of filtration and pumping is on the tank. Sounds similar to micro bubbles (doubtful though), can bubbles be seen in the eyes or are they fluid filled?