I've compared the Pocket Lighter Meter by Nuwaste Studios to my Seikonic L-558 and with continuous light sources its pretty good. With strobes its a different story... I've never actually used it under aquarium LED's though. Give it a shot!
I use the lux on phone for comparison . Led do not show a high lux. A 10 k 400 watt m/h is over 60000. Same fixture with radium is lower at 10000 . Hope this helps . A par meter is your better choice . Do the correction for leds .