How Much Light Do I Really Have? I'm Confused

[TrixyEnigma]

Ok everyone. I took your advice and went with the T5 High Output fixture for my tank so I could switch to live plants. I purchased a Coralife Fixture, 30", that came with a 10,000k daylight bulb, and the blue actinic bulb. This fixture uses 31 watt bulbs. I'll be replacing the actinic bulb with a 6,700k bulb next week. So after reading all the stickies and the subsequent posts on lighting, I think I may have more light than I need for a low-medium light tank. My tank is a 30 gallon tall. Dimensions are 24x12.25x24. My substrate is 4 inches deep and the fixture sits about two inches above the aquarium top. According to the WPG rule, I should have about 2 watts per gallon--minus whatever i'm losing by having about 1.5 inches of overhang on either side of the tank. But what I've read says that the WPG rule doesn't work with T5HO bulbs. So how can I figure out how much light I have and what I can actually grow? I'm also trying to figure out if the fixture puts me in the realm of having to use Co2. Advice is very welcome

 

[taylorodw]

You are in mid-high light territory. I think CO2 may not be strictly necessary if you have some ferts in the tank... and perhaps used excel. But you may run into algae problems.

 

[neilanh]

Agreed, that'l put you on the edge of needing additional stuff to dose and CO2, etc. Are the bulbs controllable individually? If so, you dont have to run both bulbs for the entire day, and that will lower the total light in the tank to keep you in a lower light setup that doesn't need the extra stuff.

 

[mfdrookie516]

You could also just keep the actinic running alongside the 10,000k bulb... then you only have 31 watts of usable light

 

[TrixyEnigma]

Thanks for the quick responses everyone. The lights cannot be controlled individually. I have ordered Seachem Flourish and Excel (just in case) from an online store. Right now I'm using LeafZone and I'm not that impressed. I thought about just keeping one 6700k or the 10000k bulb, but I think that makes me low light? I'd like to stay in the medium range and I'm willing to begin a Co2 regimen as necessary. But it's nice to finally know what range I may be in so that I'm prepared. I had some idea that the T5HO bulbs put out more light than regular flourescents and T12 bulbs, but I didn't know the difference was that great. Thanks for all the input!

 

[taylorodw]

I have 39w T5 over a 30gal, and I am dosing fertilizers + running CO2. When I let my CO2 slack I noticed algae problems almost immediately. Just FYI Good luck!

Every tank is different so you may not need CO2... but with that amount of light, you will almost certainly need ferts.

 

[JustOneMore20]

I suggest keeping the actinic bulb in and running it with the daylight bulb. You'd still have quite a bit of light, so I hope some stem plants were in your plant list. A lot of stem plants will help outcompete the algae.

 

[TrixyEnigma]

I currently have the anacharis and the amazon sword planted, but the sword isn't doing so well. I knew I was going to go through a cycle after I changed my substrate to ecocomplete and replaced the hob filter with the xp2. I've been doing regular partial water changes to combat the nitrate spike, but I still got an algae bloom and my sword is now covered in algae. Could this also be due to me providing too much ligh? I still have the 10,000k bulb in the fixture with the actinic. The lighting schedule was 4 hours of light on, 3 hours off and 4 hours on again. So now I've reduced the light to about six hours total, with about a 4 hour break in between. I've also been dosing with Leaf Zone fertilizer, about 2 ml every other day. Any other suggestions? I'm thinking about pulling the amazon sword out and replacing it once the cycle is over. The anacharis is doing fine.

 

[mgamer20o0]

swords are heavy root feeders so it should just need a root tab to help it out. you can also raise the lights a little more so less light gets into the tank. next time i would check out try ferts. dry ferts are about 22x cheaper generally. you can get about a year plus supply for the amount you paid for the Seachem Flourish. Excel i believe is known to melt anacharis just like it can melt vals so be careful.