Lighting. When is it too much?

[grey_fox]

Hi there,

I'm got something that's been bugging me lately. I'm bugged with a lighting issue.

When is it too much lighting for your tank? I currently have 8 x T5HOs @ 54W each, this equates to 432W in total and 2.9WPG.

Initially I thought that there minimum should be 3WPG for fantastic plant growth (how true, I am not sure...) however at 2.9WPG, my plants are growing good (along with bits of algae here and there) however, the alge is not the issue, my main issue here is that I have noticed blackish spots on my java fern leaves. The leaves which are not in direct contact with the lights are fine, its those that are directly facing the lights that receive this 'free gift'.

I saw some of Oliver Knotts set ups (large, X-large tanks) and his lightings are really little but his plant growth superb!

Tank for example one of his set ups, 500L with 2 x 80W T5 HO tubes (http://www.pbase.com/plantella/wslu05) which equates to 1.2WPG. For another of his tank, 468L with 4 x 38W Acadia tubes (http://www.pbase.com/plantella/130cm_tank2), this also equates to just a mere 1.2WPG...

I've cut down my lighting from 8 x T5HOs to just 4 x T5 HOs however am thinking if this is sufficient (downsizing from 2.9WPG to just 1.4WPG now) and would like to hear your views on this issue.

this is really bugging me...



P/S: Mods, if I posted this is the wrong section, please help to move it to the correct one and please accept my sincere apologies.

[BFG]

Grey Fox, you could just use the number of T5 you want and monitor the situation. Watched how the plants fare and adjust accordingly. How is the lights activated for your setup?

[bclee]

"wpg" is supposed to be used as a guide. There is no scientific basis for the wpg rule.

From many hobbyists experienced, smaller tanks generally require higher wpg than larger ones. A 2-ft may work with 3wpg or even 4+wpg. However, 2+wpg is already quite sufficient for 4-ft.

MH, FL, PC and PL must also be taken into consideration.

BC

[dc88]

I think it also depends on the type of plants and the rate of growth you prefer.
Some plant (such as java fern) can adapt to lower light level.
The reference you mentioned above, I noted that the plants were specially selected mostly fern, crypto and anubias, which are "low light" plant. Did you notice there is no "high light" plants (especially at the foreground) such as glasso, hair grass, etc ? Or brightly color stem plant in there ?

For your fern problem, did you able to identify it as some form of algae or plant deficency ?

I have some "Windelov" fern under the bright light that small amount of BBA at their tips which I occasionally trimmed them. Those in the shade looks much better shape.

May be you can shift the fern to the corner or side of the tank (which usually at lower light level) ? Or add floating plant to shade them ?
Or if you want to reduce the overall light level, than you need to consider the whole tank plants selection and design from there.

Interestingly as BC stated, the larger the tank the wpg requirement do get slightly lower (for the same type of light and plant). There were some discussion I came across which trying to figure out why it is so. Some said that it could be for larger tank more light get reflected back to the water column while small tank more light escape from the sides. But you have to compare apple to apple. You can't take a large fern tank compare with a small amano style stem plant tank.

[brianclaw]

Try looking up Rex Grigg's site. He has a pretty good explanation on lighting requirements for your planted aquaria.

[juggler]

Maybe can read up some research done on Amano's tanks.
Lighting as a Function of Tank Size in the Aquaria of Takashi Amano .

For my 5ft tank (470L), I used to have 432W (3.4 wpg) as well. But I have lowered it to 324W (2.6 wpg) currently. I have also tried 216W (1.7 wpg) but growth was slowed down quite a fair bit.

[grey_fox]

Hmm interesting read. According to the calculation, for my 566L tank, 226W is calculated. That would roughly be what I am using now, 4 x T5 HO tubes @ 54W each which is loosely based on 1.4WPG.

So far what I have noticed is that 8 x T5HOs, the entire tank is pearling... like a giant champange 'bottle'. Pearling is noticed 1 - 2 hours into photo period. After cutting it down to 1.4WPG, pearling is still noticed 1 - 2 hours into photo period but not that obvious and bubbles are tiny compared to 2.9WPG and plants like the nanas have stomata formed but pearling is not seen anymore (might be bubbles are too tiny for the naked eye).

My aim here is to achieve good plant growth and on top of that, to stop or prevent any algaes from growing... and ultimately find the best combination of lighting for my tank.

2.2WPG the best solution? Any feedback on this?

[GaspingGurami]

Grey_Fox,

I think that just as there can be resistance built up against antibiotics, plants similarly can get "immune" to high lighting as well as CO2.

I've a 20L tank that is lit 10 hours daily by 72w PL lights. That's around 13.5 watts per gal. I get quite fast growth and no algae with daily dosing and high CO2 injection rate, but I don't have ANY pearling.

I used to think that I'm doing something wrong since I so badly wanted to see the bubbles. So 1 day, I did a small experiment after thinking back how my plants "pearled like mad" immediately after a blackout. So keeping the same CO2 injection and fert dosing rate, I changed the light to a single 18W (3 watts per gal) and ran this for 2 weeks. I noticed that growth rate decreased, green spot algae was starting to appear, fishes were gasping at dawn and shrimps were wiped out. After a fortnight of this, I went back to my old 13.5 watts per gal setup and lo and behold, the very first night of the change, my tank was a bubbling champagne bowl! Sadly, the pearling slowly petered out after a month till there was none.

I also had a 2ft low tech that I decided on a whim to introduce 500ml of CO2 a day, everything else being constant, just to "see what happens" (I used a square "liang teh" bottle with the bottom sawn off and filled it with CO2 in the morning) 3 days after introducing this, the crypts started bubbling. Soon, the java ferns, Windelov and even Taiwan moss joined in. This bubbling kept up for 2 weeks or so, then eventually it also petered out and BBA started to show up.

From this, I surmise plants do learn to "switch off" when it has too much of a "good thing" which in these examples are Light and Carbon. I've been considering lately to slow down on the light, but I'm not yet prepared to face the transition period where algae comes to visit until a new equilibrium is met.

As for the topic of smaller tanks need more light, I agree with this totally. I've never been successful growing HC on the gravel of my 13 WPG tank, but it literally is a noxious weed multiplying and covering half the surface of this same tank within 3 weeks if allow bits of them to float on the surface. I think it is due to the fact that light is less diffuse when the light source is nearer in such a small tank, so even more light is needed to penetrate the dark shadows cast by overhanging leaves.

Having said this, I must qualify by stating that I have a huge Echinodorus covering three quarters of the tank that is casting great shadows beneath it. Perhaps if I were to grow only HC in this tank with no plants to shade it, I can do with much lesser watts.

Lastly, I concur with DC88 about low light plants. So far, I've never been able to grow Java fern nor Anubias out in the open of my 13WPG tank and not have algae on the leaves. Regardless of the amount of CO2 or ferts I dose, they just can't grow fast enough to beat the Green spot algae and need to be shaded in order to stay totally algae free.

And this takes time to establish how much "shade" to get that equilibrium. Meanwhile, I wish you good luck and patience.

[grey_fox]

Hey Lawrence,

Thanks for that delightful insight. Not to be fickle-minded but I guess jumping back to 2.9WPG would be alright it seems. Something I have noticed too is that normally the smaller tanks indeed need more light and bigger tanks lesser.

Can you imagine if you used the 432W of T5HOs on your tank? Anyways, something I need to be clear about.

Bright/high lights in a big tank, does this contribute to algae growth?

[GaspingGurami]

Bright/high lights in a big tank, does this contribute to algae growth?

Until you find the equilibrium of CO2, fertilisation, growth and circulation for your tank, you WILL see algae, regardless of tank size. High lighting reduces the margin for error, making the quest for an algae-free tank more tedious but still possible. Just don't be too quick to micro-manage the tank as plants need some time to adapt too. And after they're adapted, you sometimes need not change anything at all.

I've no experience with big tanks since my biggest tank is 2ft. But I notice that the bigger the tank, the more forgiving it is on dosing errors but the more tricky it is on getting even circulation to ALL areas of the tank