The de-facto champs for all out CRI and efficiency are Bridgelux Vero Decor series..
Sets of ww/neutral or cool white is all that is "really" necessary.
high efficiency, low price but w/ some, as you know drive current liabilities..
They can far exceed the output LDD's (up to 4200mA
)can deliver in many cases.
Second downfall is thermal management of such large yet dense arrays of chips on board..
Passive cooling at high drive currents is "problematic"
Third downfall is getting decent lenses. Proper placement and even for a deepish tank not really necessary..
All of the above can be remedied by $'s though. But kind of defeats the cheap chip thing.
One of the reason small emitters are still popular. And of course the VERY cheap prices of cheap 3W chips, even if you need 2 or 3 to one compared to name brand emitters.
Since aquariums are more of an afterthought in the manuf. world all have compromises. The large COBS are designed around OEM canned lighting uses.
On the small end little .5W smd's (much harder to work w/ for DIY) are exceeding 200lumens/watt and rising.
These are also targeted to "architectural" or home use..
But for us the large dense arrays of small emitters on circuit boards are not easily worked with.
One chip I would die for to have on a 4' board are the Yuji smd5630's that use a violet "base" emitter and phosphor pack for >95CRI..covering ALL wavelenths of visible light for the most part. No cyan shortage, no "violet" hole..
The point is, since none of these things takes DIY and aquariums seriously the "best for our use" will be some accident in creation..
I don't even want to get into the individually "addressed" diode strips which could actually allow "zoning" in an aquarium.
Currently DMX based for stage and advertising ect.
There are probably a dozen "innovations" that have crashed in prices and are, in some form or another usable but just hasn't hit any type of density...or has been well thought out.
I've discussed and seen working large , greater than 3A custom drivers ala LDD style ..and Meanwell and inventronics and make large ones as well but mostly as ps/drive "units" w/ a price to match.
On a more specific note "if" you can get them for a cheap enough price (or even get them..) pairing this:
BXRC-56G4000-F-24 5600K 90 CRI 113lumens/watt at @1050mA
28.8v and 30w/chip w/ a low k chip..
BXRC-25E4000-F-24 80cri 2500k 118 L/watt at 1050mA and 31W/chip
Both run full on effective temp of approx 4050k w/ a good deal of red and even a bit of a cyan boost is pretty much all you need.
Color to taste..
Each cluster will run approx. $30. Add 2 LDD's for $16 and you get $46 for 7000 Lumens per cluster..
Equiv. to 70W of T5's in a tiny package..(on a lumen basis, PAR is different, as is "delivery" geometry)
for your tank you'd probably want 6 "sets"..$276 plus asst. parts and power supply..
Oh and easily pushed up w/ 1500mA drivers..losing a bit in lumens/watt but gaining watts..pushing the 2 chips up to 3 t5 equiv. approx..w/ no extra cost w/ the proper ps. Adds 10W each to the chips..500w ps guesstimate..at 36V but only a ballpark figure..
Add a RGB to each set for fun...
Oh and just because a chip can "take it" doesn't necessarily mean you should give it..
Oh and you can modify a TC-420 controller to run the whole thing.. $25-$30 usually... 5 channels..
It would take 19 CREE l2's to equal 1 cluster (375-ish lumens/1000mA) .. though at your price.. Under $56.. What color temp btw..?
you would need to push them to 3000mA to get close to 10W out..and may hit 700 lumens/chip but good luck w/ that..
The cost would be around $30 (10 chips) for a "cluster equiv" at 1000mA vs 3000mA
down and dirty calcs..and throwing out the 50W-er all together..
The Bridgelux at 1500mA is almost 5000 lumens/chip x12.. Grand total of 60,000 lumens over your tank..
20 4ft led shop lights..