I hope the M series works out OK for you, but I think you'll want it pretty close to the top of the tank. I have one on a 40 gallon breeder I'm using as a farm tank, and while it's OK, it's just not powerful enough to give me the growth and color I want. My comparison lights are a Fluval Plant 2.0 which it beats by a mile, but it can't compete with my Chihiros WRGB 2 which isn't a fair comparison based on wattage. I've now ordered an L series which should be on par (pun intended) with the Chihiros but at a much better price.
Mines a pretty shallow tank, around 10 inches tall, which the Week Aqua International site seems to recommend.
WEEK AQUA INTERNATIONAL
My previous light was the A2 Series 601. Had the A2 on 100%, this have started at 80., see how it goes. Its sitting on the rim of the tank.
Haven't played much with the presets, went with the white mode, maybe has im used to it from the whiteness of the A2, and adjusted up the red a little more. I have a cheap light( neo Helios xp) on another tank that makes the Ludwigia Arcuarta tips so RED. and wasn't happening with A2 at all, hence trying the M series.
Its only been a few days with the M series and already im getting some good red coming through.
Maybe its moving into the world of RGB's, and proper lighting !!!
Definitely keen to get another Week Aqua, L or M, for another Tank I have.
I know they are very cheap on Ali express, but no or limited warranty, was going to purchase from the internal site, as there isn't, well wasn't a lot available here in AUS, a random FB pop up post from a wholesaler mentioned some of the newer models had arrived. turns out a very local store were due to get some, so purchased from them, slightly higher than the international site, which didn't include a shipping cost.
So happy support them, they are one of the few places that do C02 refills, instead of swaps.
Think I will do a Nature Style scape with A2 in another shallow, maybe the
ADA 60F or similar has it looks ok on mostly green aquascapes.
As for the initial set up, dimensions I rechecked and was close enough with the inputs, but interesting if it really does adjust. as the spread across the the tank width ok, but could be some big variances in substrate levels.
The L series does seem like a good fit for your 40 Breeder, hopefully the link works I posted, the site has some good info.
ive yet to dig in and see what the UV is all about, I know on the current setting its on the 0%,