Sansevieria?

How long have you been growing them under your lights?

Maybe (?) other growing conditions are coming into play (e.g., growing medium, impaired root function, etc.)?

I keep 3 dwarf Sansevieras (hahnii, laurentii, and some type of bird's nest variety) in front of a west facing window that receives diffused sunlight. Although they are slow growers, they have grown steadily over the course of three years. Have not measured LUX from that window recently, although measurements taken in the past were approx. 1000-1500 Lux on a good day, at best... the reason for mentioning (above) other possibilities, besides lighting, coming into play.

A four-tube T8 fixture should provide plenty of light for most foliage plants, especially Sansevieria.

I've had several do fine and grow steadily under both T8s and T12s (which probably provide even less output).

For sansevieria it pretty much guaranteed not to be the lights. They are pretty much bullet proof. Only thing that really kills them is too much water.

Most people on here overestimate the capabilities of shop lights.n they do grow things but much slower than youll be lead to believe here. If you want some real noticeable growth youll need an HID light.

Khaled

Yes indeed, HID is the choice of many for their lighting applications. But ~ OP "I'm not interested in nor can afford HPS or similar. I use only T8 32w bulbs."

You bought the wrong bulbs. You need daylight bulbs @6500k such as these:

Daylight 2-pack

Daylight 10-pack

These are the exact same brand of bulbs you are excoriating as "awful", under which I am successfully growing over 20 M. koenigii - curry leaf tree, a member of the citrus family. Except they are 6500k daylight bulbs. The bulbs you chose are most likely around 3000k (warm) and 4000k (cool).

I too once made the choice (many years ago) to try the warm/cool combination and it did not work. I had the worst growth ever with that combination. Still the myth of the warm/cool combo persists.

However in this case the problem is not the wrong bulbs. Sansevieria does fine without any supplemental lighting AT ALL. Whatever the issue is it has nothing to do with your lighting.

You do realize that Sanseviera growth rate is pretty slow. Over what period of time have you decided they aren't growing "fast enough"?

yes @zensojourner,
I bought the phillips brand warm white 3000K and the phillips brand 4100K cool white. both were the twin packs at home depot. yes worst growth ever. the day I went there they had in twin packs- warm white 3000K, cool white 4100K crisp white 5000K and daylight deluxe 6500K. at the time I was overwhelmed didn't know what light was best for maximum growth on any indoor plant, I had a four tube fixture just dying to have tubes lol. so I went with the wives tale that to have a quote full spectrum of light buy warm white tubes and the cool white tubes. ya never again lol. so yes ill take your advice and buy all 6500K daylight deluxe and use them as the only light in the fixture, (I got some nice oxalis bulbs sprouting in pots as we speak in a SE window. thinking of buying the 6500K tubes and growing them under that :) and the good thing with daylight deluxe means with the added benefit of being 6500K the deluxe means they have a small amount of "red" in them which will help them to flower good. and yes ill admit I got cheap buying soil.. I had a tendency to re use soil each time I repotted a plant, when id shake some soil loose from the plants roots id put it back in my soil container. (I use a large under the bed tote for my soil. I just keep buying soil adding to it, when I repot a plant ill shake off some soil add it to the soil in the tote. but I think that's bad, I noticed because the tote stays sealed so long, I noticed on the inside lid of the tote theres a lot of condensation probably not a good thing. probably means even though I cant see it visually, there is probably microscopic mold in the soil in the tote and scrapped all the soil in the tote!! and stopped being cheap, and went out and bought the good soil to use on all houseplants- promix potting mix (the purple bag) all purpose. I now use it straight out from the bag. love it, think my plants will love it too!. is that one of the best soil to use on any houseplant minus a cactus or succulent lol? I know miracle gro soil is no good and stay away from it unless you want dead plants and fungus gnats through your house! but is that purple bag promix great stuff for most houseplants minus cactus and succs? and your saying just buy and use all 6500K daylight deluxe tubes in my fixture right? I usually aim for 16hrs a day with the four tube placed close to plant tops so my light meter reads 6000 lux or higher for 16 hrs day

Actually I'm not a Miracle Gro hater. I have used and do use MG on occasion, but lately I've been working to find a new mix for my container soil since I can't get coarse grade vermiculite any more (and haven't been able to get it for over 10 years). Currently I'm testing a 3:2:1 bark:peat:GrowStone mix. (I use GrowStone as a perlite replacement)

I have also used a fairly complicated mix that includes pumice and DE intended for use to help turf to dry more quickly in addition to the bark, peat, and growstone, but I really only did that to use up the gritty-like mix that I decided I didn't like.

I have never had fungus gnats with MG in any of its incarnations over the past 40 or 50 years. I think people just tend to overwater it. Since I'm a chronic UNDER-waterer, I've never seen the problem.

Yes, keeping your old potting soil is bad. The organic components break down over time. Even perlite will break down over time, and many potting mixes use the smaller grade of perlite to start with, which is already Not A Good Thing. I usually dump my spent potting mix in the compost bin. I have, in the past, recycled container mix 50/50 with new - but only in outdoor, large containers growing veggies. Never for houseplants.

I've never used Pro-Mix myself, but I've heard its a good mix, as premixes go.

Yes, I use all 6500k bulbs in all my fixtures. There may be something out there that would benefit from a different bulb, but whatever it is (if it exists), I don't grow it.

I've been using T8s for years. 4100Ks are the worst bulbs. Warm/cool is fine but you need 3000 and 6500. As a single bulb I like the 5000K. The price on those has increased a lot.

Since you have them, try using 4100K tubes as the only light source in a room and you'll see why I hate them.