Mars Hydro FC4000 vs Spider Farmer SE4500: Side-by-Side Test

Last updated: September 2026.

Put these lights next to each other and the first question is obvious: are they basically the same light wearing different shirts? The components, screws, bar markings, diode counts, spectrum and even the shipping origin were so similar that I wanted to stop guessing and measure them.

I tested both lights in the same 2×4 AC Infinity tent, used an Apogee MQ-500 at six canopy locations and kept the sensor 18 inches from the light. I also let each fixture stabilize for an hour before comparing heat. Same room, same method and no brochure math.

Jump to the comparison

• 0:00 — Why these lights look related
• 0:29 — The controlled test setup
• 0:53 — PPFD readings
• 1:33 — Heat after one hour
• 1:56 — Spectrum and LED count
• 2:15 — Edge distribution and dimmer differences
• 2:52 — My winner

Selecting a timestamp opens the standard HWGrow pop-out player at that exact moment without making you lose your place on the page.

What was almost identical

The heat difference was basically nothing. The Spider Farmer used about four more watts in my test and produced slightly higher PPFD readings, so the tiny temperature increase made sense.

The small differences that decided it

The Spider Farmer pushed more of its LEDs toward the outer edges. That matters in a 2×4 because weak corners are one of the most common problems with narrow fixtures. The center of a tent is easy to light; keeping the outside of the canopy productive is where the design earns its money.

Both lights had continuous dimmer dials and could turn all the way down, but the Spider Farmer also displayed the exact percentage. That sounds minor until you are trying to repeat a setting after raising the light or starting a new cycle.

Which one would I buy?

If both were the same price, I would choose the Spider Farmer SE4500. The edge distribution was better, the test readings were a little higher and the percentage display made the light easier to repeatably control. If the Mars Hydro is meaningfully cheaper when you shop, the test did not expose a huge performance gap; it is still a close comparison.

Prices and model revisions change, so compare the exact listing—not just the familiar model name. My old-versus-new Spider Farmer investigation shows why that warning matters, and the indoor grow equipment buying guide explains how the light fits into the rest of a complete setup.

Compare the exact lights

Spider Farmer SE4500My winner in the side-by-side test because of its stronger edge distribution, slightly higher output and percentage display.Buy It Now
Mars Hydro FC4000A very close alternative with nearly identical dimensions, diode count, spectrum and stabilized temperature in my test.Buy It Now

Affiliate disclosure: HWGrow may earn a commission from qualifying purchases at no additional cost to you. Product listings can change, so verify the exact model and specifications before buying.

Next: See why an old and new grow light can share a name but not the same specifications