Improving The Lighting On My Pfk Cube

[nry]

My PFK cube (5.5 UK gallons) has been lit by an Interpet Daylight Plus 18" T8 tube plus reflector for months now. I have vallis mini-twister, anubias and some pretty much dead u.gramnifolia.

The vallis is not doing 'that' bad, but it certainly isn't doing as well as the same plant in my 15gallon.

My PFK cube has:

EcoComplete
Daily doses of Flourish, Flourish Trace and Excel based on the weekly amount/7
Weekly 50% water changes

I am now doing EI on the larger tank so I am close to using the same fertiliser regime for the PFK cube aswell, though reduced accordingly for Excel and not CO2.

Would a T5 Power Compact at 24w be sufficiently higher than the T8 to be of any benefit for this tank? I think the higher 36w tube (16") is possibly overkill but I am not too sure on lighting levels for smaller tanks?

Advice welcome, so far it is not looking as good as I was hoping to get it into the PFK competition in a few months!

 

[DevUK]

I'm guessing you'll have issues going higher than 24w due to the size of the tubes. 24w is 12" I believe. They get longer for 36w (16") and 55w (21") I believe.

Am I right in saying the PFK cube is approx 30 x 30 x 30cm? I was investigating lighting for my new tank I'll be setting up soon and I calculated WPG and Lumens per square cm (light per surface area). The 24w daylight plus tube is 1600 Lumen. So working out your WPG and Lumen per cm2:

24w/5.5gal = 4.36wpg

or

30x30cm = 900cm2 surface area of tank

1600 lumen / 900cm2 = 1.78 Lumen/cm2. I think that this should be plenty

Compare this to what you have now (not 100% on which tube you have):

18w/5.5gal = 3.27wpg

or

1300 lumen / 900cm2 = 1.4 Lumen/cm2

I take this method from George Farmers fantastic post explaining this. Hope it makes some sort of sense I'm still trying to understand it myself...

Edit:

Just noticed its 18w tube you have, adjusted for that

 

[nry]

I am likely due for a new tube anyhow, I think the current 18"/18w T8 is over 6-months old now, and has a number of areas which are dark/discoloured. The fact that 8" of tube is not directly over the tank probably doesn't help either! Going to a 24w 12" tube should be a decent improvement, as if nothing else, the whole of the tube length is directly over the water.

 

[Castellop123]

...

 

[nry]

Yep, that seems the best plan, I shall await pay day