Best way to attach Shelf Brackets on a Drywall for hanging Light Fixture without using Stud?

Question

I'm looking to hang a 4ft T5 fixture for an aquarium to a pair of shelf brackets on a wall. I'm looking to mount it without using a stud if possible, maybe using a toggle bolt or drywall anchor.

I'm wondering if toggle bolts/drywall anchor would be strong enough to hold shelf mount + light fixture. Ideally I would want each one of the shelf brackets to be able to comfortably hold the fixture, in case of failure on either side.

Total weight will be about 20lb, but the fixture may be adjusted up and down on a weekly basis, so it may put more strain on the wall. The light will hang close to the end of the shelf mount, if that matters.

I'm trying to avoid using a stud because:

1. Studs are not located where the aquarium will be placed. (Not much flexibility for the location)
2. I live in a rented apartment where the contract states I cannot drill into any wood. This seems to be for doors, etc but I want to err on the side of caution. Our building manager recently passed away and the interim building manager is hesitant to give any conclusive answer.

I'm not much of a handyman, so let me know if I'm missing out any important detail and I'll add them on ASAP. Thanks in advance!

Links to items below. A better suggestion for a shelf bracket that's 14+ inches would be appreciated too. Going for a relatively sleek look if possible, but safety over looks.

T5 Fixture - Shelf Bracket 1 - Shelf Bracket 2

Answer 1

That's a quick drawing of a shelf bracket set against a wall.

This is basically a bent lever, so if the weight of your light exerts a force F1 on the end of the bracket, which extends a distance A from the wall, then the bracket will pull on the anchor with a force F2 = F1 * A/B

TL/DR: pick a bracket with a long vertical part (B) to minimize the pulling force applied on the anchor.

Since both your brackets have B shorter than A, the pulling force on the anchor will be higher than the weight of the light fixture. Therefore, you might as well stick the anchor in the drywall ceiling instead, and forget about the shelf bracket. In this case the anchor will only bear the weight of the fixture.

Answer 2

I have installed TVs on drywall using snap-toggles. Also put up much heavier curtains using drywall anchors. I also put up a few light shelves using drywall anchors.

20 lbs is not a lot of weight to support on 4 anchors. Toggles, especially on the part of the anchor that is being pulled away from the wall, will help increase that significantly.

The major concern is that the light appears to hang from the shelf bracket -- dynamic rocking loads will cause wall anchors to fail; this won't matter if you don't hit the light when tending the plants.

Here's a good article explaining the limits for different kinds of anchors: https://www.naturalhandyman.com/iip/inffastener/infanchor/infanchor.html

Answer 3

Why not buy a free-standing scaffolding or stand to hold this light. This would give the option to move it in the apartment or take it with you when you move. A Google search indicates these are widely available.

This might save you a damage charge.