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I think I would prefer the old style trough tanks, as you actually can see what's going on without opening anything, and thus this will enable you to pick up a problem hopefully before it becomes a disaster. It's a pity you are not closer as I have 4 of those laying around unused including 4 trays each.

Stress due to on-off switching of pumps is mainly a result of high inrush currents at start-up. If you put a soft-starter or a vsd (speed drive) before a pump you limit this wear substantial. Obvious this is most relevant for larger expensive pumps. If you need a pump of less then 100W I wouldn't worry too much about start-up wear. Dry or submerged installation has both positives as well as negatives. My general advise; Small pump submerged with a magnet drive, bigger pumps dry installation, pump with shaft connecting motor & pump. Waste water pump submerged, as suction head tends to be low due to larger space between impeller and pumphouse.

Nicely done with the laundry baskets, although seems like a lot of work to make. As an alternative you can use 50 mm pvc to make a floating frame, covered with oyster mesh, fixed with cable ties. Make them big enough so a box grader fit in and you can grade on size within 1 tank.

Hi Ande, Excellent find, although I have seen a number of these publications already.

If you like flood and drain, a timer on the pump, and a double overflow (restricted bottom and unrestricted top overflow) will work more reliable than a bell syphon.

Hi Pita, Hard to advice without seeing the actual configuration, but I don't think size of tubing is the problem as velocity in pipe is high enough. In general raceways have poor self-cleaning properties (one of the reasons to choose round tanks). You can actually improve self-cleaning abilities by creating circular flow in sections of the raceway; they call this design mixed-cell raceway, see https://cals.arizona.edu/azaqua/ista/ISTA7/RecircWorkshop/Workshop PP & Misc Papers Adobe 2006/4 Culture Tank Design/Mixed-cell Raceway/Labatut 2005 - Aqua Eng - Hydrodynamics.pdf

Hi Ande, You right this looks like an old hydrotech. I had a couple of those installed at a farm I managed back in 1989 (I think).

Hi Moses, fyi, T5 florescent are the most used lights in Indonesia. I wonder, why do you need artificial light while you on top of the equator? as this guaranties sufficient light the whole year. Going to be hard to beat the sun, and electricity is quite expensive in indo.

Hi Moses, Which island; Nias or one of the Mentawi islands? I actually recently visited West-Sumatra and the Gramedia I mentioned was in Padang. Years ago I lived and worked in Padang so I do know Sumatra a little bit. Ande, I do think that Moses his first language isn't English (btw neither is mine) and that's why I advised him to check out local resources.

Hi Moses, In which part of Indonesia are you living? Might be a good idea to check out your local Gramedia for books on aquaponics, I was in Indonesia last February and they carried some good books on the topic.

Yes should be fine; rinsing with water, followed with a bit vinegar is all that's needed.

Hi, As a technical minded person active in the industry I am always interested in new technologies. Thus had a look what the Akva group has in their online add. While it might be good equipment there is nothing new here, uv; partial flow, full flow all has it's place in the aquaculture industry; I use both set-ups often at the same farm in different modules with different aims. Drum filters, again not new and or innovative at all. The new line of hydrotech drums has some interesting features, and seems to get away of rotation on demand, replacing it with slow steady rotation. As for European build RAS equipment, the best stuff is made here!! (me too but that's not related). If you can't find it you look at the wrong places, look in a aquaculture magazine and you will find lots of stuff. But don't understand me wrong, the fact that it's made there doesn't make it affordable. My favorite drum filter brand is Faivre (france) build like a tank, last forever but priced accordingly. btw I have a small faivre in my home system for more then 4 years and haven't touched it besides greasing bearings 2X a year and cleaning nozzles with the same frequency. As for Valodja, I mentioned this before, your plans are big and you seems to be inexperienced, please get a professional opinion before you commit to big spending's, and I don't try to sell myself here as nowadays I live in another part of the world. Another thing is is that on forums ideas move like waves of fashion, now it's sand beds or dual loop while before it was something else. Many configuration can and will work, if the operator has the skills, motivation, character and financial back-up (if it's commercial)....

Thanks VKN, No it's not to late, I might try to run a feeding trial with snails for barramundi. So this are apple snails, which you grow on plants? Do you just feed some of these every day? any idea on impact?