What lights on your 20L tanks??


New member
I have PC lights by Coralife, called the Lunar Aqualight, and I'm wondering what you guys think. It has one 65 watt actinic, and one 65 watt 10,000k daylight, and two lunar lights. It also has a cooling fan built in to the hood. I have heard that 10,000k bulbs might promote more nuisance algae and it would be better to have a 14k bulb. I am having problems with cyno and a bit of green algae, and between twice weekly water changes and reduced lighting schedule (6 hours of daylight bulbs, 8 hours of actinic) it has been dragging on for many weeks. I find that with such a shallow tank it is tricky not giving the tank too much light that promotes algae outbreaks, however gives my SPS and LPS enough. Another problem is finding any good lights for a 30 inch long tank. :(

Please tell me what you have on your 20L tanks, what corals you have and if you are pleased with it. Thanks!


New member
Hi sue711 :D

I also have a 20gLong. I have a 20" Sunpod (150w MH) on mine. The bulb is a 14K Phoenix and i have a mixture of sps, softies, and an rbta.

In regards to the length issue of having a 20" long fixture and a 30" long tank, I have kinda rigged the sunpod by simply using 2 rails that cross the tank front to back (not end to end) and the sunpod sits directly on it. I was originaly worried this wouldnt have a good enough spread of light, but actually works much better that i thought. So you could actually go with a shorter fixture if you needed too. (24" fixtures look very close to filling the whole length) www.marinedepot.com sells some really nice T5 fixtures that are 30" in length. They are 2 bulb nova extremes and my buddy has one on his 20g long. They are very well priced for how well they're made! Here's a link...


The second issue is the depth/shallowness of the tank. Because the MH unit is actually so close to the sand bed (only about 14" i'd say?) I too have had some struggles with algae outbreaks. With the spread of light being really good, but the ends of the tank being just a tad not as bright, the ends of the tank have been optimal places for my corals starting out. I've had to keep them on the sides and slowly move them into the middle of the tank. At least those that can handle being direclty under the MH so close.

I personally think your fine with the 10K bulb and the actinic. I really dont think changing to a 14K would change much as far as algae growth. I do believe that by you dropping your lighting time to 6 hours daylight will help.

Another thing you may want to try is doing "3 days of darkness" on your tank. I've done this myself, and know many others who frequently us this method to help with algae. It wont hurt your corals or fish in anyway. All you do is simply turn all your lights off for 72 hours. (including the moonlights, turn them off too) Your corals and fish will just think its a few cloudy/stormy days at sea ;)

HTH - Good luck! :thumbsup:


New member
i just use a 150w pendant from fishneedit. i just recently replaced the bulb with a phoenix 14k and keep mostly just softies and lps. The feet that come with the light are enough to keep it about 4-5 inches off the water.


New member
Jadams, thank you for your very thorough response! :) I don't think I want to go down the MH route, because then I'd start to worry about heat issues, and I already spend too much energy thinking about worst case scenarios. ;) When I get a bigger tank (I can dream) I definitely will have MH lighting, but for now I think my best bet would be something like the T5 you mentioned or similar.

I haven't tried the lights out recently, I did a while back but it was only for two days and I worried about the corals the whole time. I may give it another shot, but add another day to total three. I have read that people have success with this, but I wonder if it only helps short term.

I do think that keeping the daylight lights reduced to 6 hours a day has helped cut back the algae growth, but I wish I could see my tank lit up more during the day. When you think of it, six hours is not very long, and although the actinics are on longer, it just isn't the same.

Now I know why they say Nano tanks are tricky. Not only are the water parameters more sensitive, but every aspect from water flow, feeding, to lighting requires careful consideration because it is so easy to overdo it in a nano.

I appreciate everyone's input! Thanks all.