That would be a 48" t5ho 54w actual bulb length is 45ish inches. Google 48" t5ho in 10k lots of places sell them. I've found it hard to find 10k bulbs in the high output anywhere but aquarium specific sellers. No or normal output won't work in your fixture as no is a different actual length and wattage. I used t5ho on my reef tanks for years before switching to led.