Lighting And Depth

[KPD]

Hi all
I was just working out my watts/gallon, and they are in the low range. In part this is due to the depth of my tank, at 2ft deep. It seems to me though that although light spreads out with distance, internal reflection of the tank sides keeps most of light in...so msot of the light reaching 1ft down also makes it to 2ft down. The area of the bottom of the tank is the same regardless of depth...so is the watts/gallon thing an approximation and not true that you need twice as much light to light a tank that is twice as deep?
The lighting is 2x80w t5 over a 200cm x 60cm x 60cm tank.
Thanks
Kev

 

[SuperColey1]

2ft is not seen as deep. More than 2ft then more calculation/experimentation is needed. Therefore you could have used the WPG rule as per a normal, sized tank. However in your case the WPG rule is useless because:

1 - You are using T5 tubes which can be as much as 2x the WPG rule
2 - At 190USG your tank is very large and the WPG rule is basically only for average tanks of 20-40USG.

You currently have 160W over a 190USG tank which means you have 0.9 WPG. With it being T5 it could be the equivalent of 1.8WPG by the WPG rule. As a guide I use 0.9WPG of T5 over my 125Ltr tall (20inches) tank. I also add 0.6WPG of T8 for 2 hours in the middle. I have no problems with any plants growing so the light must be good enough. With your tank being so large then you don't need as much wattage as a smaller tank and therefore I can't see any light problem with your tank.

The tank sides will not keep the light in!!! don't understand this statement.

Do you see light eminating from the tank onto the walls? If so then this is light escaping which you will always get!!!

So please stop worrying about the height of your tank.

Andy

 

[KPD]

The tank sides will not keep the light in!!! don't understand this statement.

Andy

Sorry...didn't explain myself very well
Internal reflection always occurs with light hitting glass (or any transparent surface where there is a change of density) at an oblique angle. You can see this in action with your tank....press your face up against the glass and look up...you can't see the lights above the tank from the sides becasue the light from the luminaire can't leave the tank directly. The light that does escape from the tank is the light that bounces off the objects inside the tank, hitting the glass at a much lower (closer to 90 degrees) angle.

Thank you for the reasurance on the watts/gallon thing
I shall focus other things...this weekend is trying to get my CO2 injection going....I'm sure I'll be back with lots of questions about that....and then when that's running I'm sure I'll have to start playing with nutrients

 

[SuperColey1]

There will always be some light loss no matter how good reflectors are or tank is but I don't really think it matters too much.

Just to reassure you on the light this is my 125Ltr (80cm long by 45cm tall) with pressurised CO2.

This picture has both lights on so 1.5WPG in total (0.9WPG T5 + 0.6WPG T8) This is used for the middle 2 hours of 10.

Blyxia Japonica which is the light green midground plant I have used along the length of the tank is supposedly a difficult high light plant and 1.5WPG would plant my 33USG firmly in the low to medium bracket so you will see what I mean by ignoring the clamour for 3-4WPG.

It doesn't look low light to me!! Does it to you?

Good Luck

Andy

 

[KPD]

wow....that's sparkling clean. What's the plant on the left (some kind of lilly)?
Kev

 

[SuperColey1]

Thats a Nymphea Zenkeri 'Red. The one on the far right is Nymphea Zenkeri 'Green'

These are the 'real' Tiger Lotus. A lot of people call theother Nympheas Tiger Lotus but their leaves are nowhere near as spectacular.

I will post a close up tomorrow to show what I mean.

Thanks for the comment on the cleanness. Tetratec EX700 with only half the media in it (Top tray has some Supawool. 69p from Wilkos) and the second tray has 2 foam pads. Tryas 3&4 empty.

No need for too much filter media in a planted tank once it is established as the plants will do most of the filtering. The media is backup.

Andy