MINIMUM amount of light for HC

[turtlehead]

I am about to set up a 38 liter with 28watts of PL light. Do you guys think that will be enough?

[taz_boy]

yes....38lt is approx 10 gallows, which mean u gonna have 2.8WPG, but if u wan consider to get plants that need high light requirements, u can try up ur lighting a bit more.....

[turtlehead]

This is going to be an all HC tank so will that amount of light be alright?

[GaspingGurami]

I've got HC living in 13 watts of light over a 1ft low tech cube. That's 1.8 watts per gal. The HC are surviving but not pretty — skinny and long, preferring to grow upwards than to creep. I think you'd not like the effect.

Tropica claims HC makes few demands, and gave a "low to very high" light requirement range.
http://192.38.244.204/productcard_1_...48B&mode=close

However, their AquaCube runs a 10-20 watt halogen over 8L of water. That's a whopping 9.5 watts per gal if it's a 20W lamp! In their article:
http://www.tropica.com/article_fulls...quacube&id=600
Their HC pearls without CO2 under this amount of light, with only an asian doormat (coconut fibre) for substrate!

[brianclaw]

I really don't think that the whole WPG rule works on tanks smaller than a certain size. I had 36W over a 10 gallon with no CO2. I also remember reading somewhere that Halogens shouldn't be treated the same way as normal lights... Something like, a 20W Halogen only gives off 1/3 of the rating. A 20W is only equivalent to 7W, or something like that...
Rex Grigg's Lumens per square inch would be a better way to measure what you'd need for your tank's size. Granted, it is hard to find out the Lux rating of your light tube(at least it is to me) unless it's printed right there on the light's packaging, but it is a better way to figure your lighting needs.
Correct me if I'm wrong, please.