Hi guys, I'm new to this forum, but, I would like to let you know how I solved this issue with the Marisys 240 Series 2. I spent about 10 hours getting this going on my Aqua One 980 tank. I had the same issue that most of you were talking about.
I was instructed by the guy I got this from, to prime it (albeit it is supposed to be self priming) by adding tank water to the rear of the filter head unit.
Tried this for hours, didn't work.
I tried siphoning water from the tank into the rear of the head unit, to keep a constant flow.
Same result, that is, the unit would pump our bubbles and water every 5 mins or so.
So I looked at the tank/sump unit. It appeared to be filling up slowly then releasing water and bubbles as it reached half way between the minimum and recommended markers.
Now I did fill this to recommend before turning the unit on.
So I removed the sump cover and used two air hoses to siphon tank water straight I to the three section filter.
Still same result although the bubbles and water came a little faster, I continued to also add water to the rear of the head unit. This returned longer bursts.
I had about enough of it at that time and finally I grabbed one of my gravel cleaner siphons and placed the tubing into the unit, on top of the blue distributer (top section with bunch of holes into) and fed the water directly into the overflow unit. (Probably could have just as easily fed it straight into the overflow from the top but as I couldn't see thru the dark plastic I had no idea how it would travel.
Anyway, with the water feeding into the dark overflow area from the top of 3 part filter, the water started coming out the duck bill constantly.
The water level automatically made it to the recommended marker in the filter section.
I let this run like that for about 10 minutes then stopped the siphon flow.
The unit runs perfectly now, and has done for 3 days. The tank is clear as a bell, and the protein skimmer is working industriously.
I added a 600 ml water bottle to the protein skimmer overflow.
And all is well. If anyone really wants it, I can make a short YouTube video of what I have just explained.
But that's how I solved the issue. I bought the unit second hand, so I didn't get any destructions. Searching the web, there is pretty much nothing explaining how to get this thing going, and I can truly understand people's frustration.
There is nothing on YouTube either.
Hope this helps guys