Do lights need to be on 24/7?

[markus]

I set up three 10-12 gallon plastic tubs and hung a twin tube 48" fixture over them. Figured I could speed grow some live plants to sell in the store since our wholesaler doesn't carry them.

Split an order of hornwort among the three tubs - one's growing really well, the middle one's okay, and the third's barely hanging on. Added guppy grass and java moss to all three, but those aren't doing much - might be dead in the last tub. Java fern's in the first two tubs, but who knows if it's working since it takes forever to do anything.

Dropped a pot of dwarf lily into the first two tubs today. Not happy with the growth, so I'm swapping the lights for a Hyper Tough 4-FT 10,000 Lumen LED shop light next week - 100 watts.

Now I'm thinking:
1 - Should I stick with the 24 hour light schedule?
2 - Any more plant suggestions for a bare bottom plastic tub? I've done anacharis before, but it gets those white roots everywhere if it's not standing up. Might upgrade to gravel later, but for now I want to keep it simple and use the tubs for raising livebearers, snails, and maybe shrimp later. Got my first snails already - they came in with a plant shipment and are multiplying like crazy. I'll add some fancy types later to snack on the sides once I figure out which ones won't eat the plants. Was hoping the java moss would attach to the sides and establish a colony I could harvest for sales.

[Snout]

I've always assumed that running lights 24/7 wouldn't be ideal for plant growth, but I've never actually tried it.

During the day, plants use photosynthesis to absorb CO2 and produce oxygen. At night, they consume oxygen and produce CO2 - it's a natural cycle. If you disrupt this cycle by keeping the lights on all the time, wouldn't that throw off the plant's biological functions, like how they use starch?

[markus]

I was initially drawn to the 24/7 lighting idea because I thought it'd eliminate the competition for oxygen between plants and fish at night. No fluctuating pH due to CO2, continuous ammonia removal, and lower nitrates were all benefits I had in mind. I had a setup with 2 60 breeders, planning to stock the top with heavy store stock and the bottom with a 24/7 plant setup. I'd read about algae scrubbers and similar concepts years ago, but I'm a bit rusty now. Trial and error it is, starting with these tubs.

The starch thing you mentioned has me open to trying a 12 on, 12 off schedule, especially with the 100 watt light coming next week. If there's science or personal experience backing it up, I'm willing to give it a shot. I had a similar tank in the 90's, but it's been so long I'm not sure if I was running 24/7 or not. I figured nutrient depletion was the biggest risk, but I've got plenty of overstocked tanks to pull nitrates from. Once the tubs fill up with fry, I'll be feeding heavy and frequently anyway. My routine would be: wake up, coffee, sprinkle some powdered flake on the babies at 6 AM, replace water at 8 AM, feed again at 10-11 AM, 2 PM, supper time, and 10 PM.

[markus]

Middle tub's got 2 full-grown female neptunes, a small male, and the snail crew. Snails get their sinking wafer daily, neptunes are fed small to oversized meals 5-8 times a day, whenever I'm feeding the tub beside them. Tested on a whim this morning - no nitrates, no ammonia, no nitrites. Not expecting any, but still nice to see. With the neptunes' feeding schedule maxed out for nitrate contribution, I'm wondering if I should start adding nitrates directly or via water changes with goldfish tank water weekly. Want to give that hornwort a boost before the babies take over.

[bettaMagenta]

In my experience, I found 18 hours of light to be the sweet spot for vegetative growth, give or take an hour. Plants just seemed to thrive with around 4 hours of darkness, it was like they were able to recharge. I recall a couple extra hours of darkness would often trigger flowering or fruiting stages in plants like water lilies or most floating plants.