How Much Light Do I Need?

[RinaLane]

I have 75G tank which was sold to me with Size 48 LED: Adjusts 48"-60" - 702 Lumens, 120 Volts, 12 Watts, 7800K Light Appearance. I have no idea what all this numbers mean.... I thought I should have 1watt per litre but here is only 12 in total which doesn't look right....
Sooo my question is can I grow some decent looking plants with this light?? I want lots of plants, healthy ones. Already spend 200 $ on big plant order it would be a shame if they all die because of light.
Also I don't know where people usually buy lamps for aquariums so I can go back to Uncle Bill's & maybe buy 2nd lamp like that because it fits my aquarium - will it help? Or this lamp is completely unsuitable for underwater gardening?

 

[DrRob]

Lighting is in one way very simple, in other ways, as you've seen from the numbers, very complicated.
 
Basically, plants need light, but too much and they run out of nutrients too quickly in our enclosed systems and the algae does better. So more is not always better.
 
Some plants need more light than others, and will therefore need more supplementation of nutrients, ranging from trace elements, to CO2 or other carbon sources, and larger inorganic things such as nitrogen, potassium and phosphorous (the same basic stuff you find in standard plant fertilisers for gardening, but aquarium safe).
 
A lot of the question will depend on what plants you get, how dense you want the growth, and how fast you want things to grow. Also how complicated you want to make it, although less complicated will restrict your options on the first few questions.
 
As for your light, it's fine. It'll grow many plants, although some will grow with sunlight from the surroundings. The numbers probably denote that it has 48 LED's, the adjustment simply how far the legs can extend, the lumens how strong the light appears to the human eye (which is sadly a fairly useless term for plant growth purposes, it does give a basic idea of how powerful the light is, but human visible light that doesn't do much for plants will bump up the numbers), the 7800K is the predominant visible "colour" of the light, generally you'll want somewhere between 6000 and 10000K.
 
Wattage is largely useless as a measure now, there's so much variation. The point of using LEDs is that they give more light out for the same power consumption (and they last longer), so the old Watts per gallon rules that we used when we moved over to fluorescent tubes from incandescent bulbs isn't really relevant any more.
 
My advice to someone starting out in planted, is to not go too crazy on the lights. Too much and you'll lose control very quickly, and you'll be farming algae, rather than growing anything nice. You'll do far better getting the fertiliser and CO2 balance right for the lighting you have, than piling on more light. So I'd stick with what you've got, let us know what you've ordered and keep it simple to start with.

 

[RinaLane]

yep i'm one of old folks who had fluorescent tubes in my old tank & had to wire them up & it wasn't fun...
 
As about plants I want. Right now in my tank is 13 anubias medium size, about 100 of Hydrophila Difformis
Have about 200 of cabomba but I dont think I'll will keep them, because they shades so bad & no roots
1 string of elodea - dont like it either
 
Will plant today
12 swords
12 Vallisneria Jungle - which is quite long do I need to cut it? Its at least 40inches long
abount 100 of each Bacopa Lemon, Lucens & Creeping Charlie
 
Can't get any other plants

 

[Byron]

Rob covered the lighting well, so I will just comment here on the plant species named in relation to light and nutrients.  But I will just mention that you might want to add a bit more red into the mix; the Kelvin number is the colour temperature (nothing to do with heat, or intensity) and the lower the K the warmer (more red, less blue) the light, and the higher the K the cooler (less red, more blue).  A K around 6000K-7000K does seem to work well.
 
Stem plants are fast growing and require good (brighter) lighting than many other plants, and with this comes more nutrients as Rob mentioned.  I'm not really surprised the Cabomba is falling apart, it does the same for me.  This plant needs brighter light and higher nutrients.  Hygrophila difformis, or commonly Wisteria, is also a fast-growing stem plant but it may (should) do better than Cabomba with less than bright lighting.  I've had mixed success with this plant.
 
Carpet or substrate cover plants need brighter light, as the light weakens significantly as it travels through the water.  If you have these plants, try them, b ut I would suggest they likely will not last long.  If your Cabomba is failing under this light, these carpet plants won't manage.  Elodea is better in cooler water, room temperature, rather than the more normal tropical temperatures, but sometimes it does well.
 
Sword plants should be fine, at least the green-leaf varieties; the red leaf need more light.  Vallisneria will probably be OK if the swords are.  This is a huge species, the leaves can easily attain 3-4 feet, and Kasselman says 7 feet.  I only tried this plant once, and it was in a tank with too little light.  Some people do cut the leaves, but I'm not sure what that achieves.  This plant does require moderately hard water, so the GH of your source water is important; if it is very soft like mine, you will need to supplement the "hard" minerals especially calcium.  This has to be considered in relation to fish species obviously, and other plants.
 
To the nutrients.  Fish foods provide all nutrients, as the waste from fish enters the substrate and is broken down by bacteria (snails help in this), and some minerals come from water changes.  Depending upon the light, and the plant species, this can sometimes be sufficient.  Without knowing your light (I've no experience with LED, still using T8 fluorescents) I can't offer much except to say that you will likely need a comprehensive liquid fertilizer.  Swords are heavy feeders, so the larger species benefit from substrate tabs as well.  I can go into this more if asked.
 
Byron.

 

[RinaLane]

Another question: is it enough to keep sunlight loving amazon swords?? I googled my lamp & description says its only good for aquariums with fish not plants

Basicaly its lowest of the aquarium lamps that MarineLand makes

 
Next one lamp with this characteristics Adjusts 48" - 60" - (24) White 1 Watt LEDs & (12) Blue .06 Watt LEDs - 1800 Lumens is good only for quote: "NOTE: These LED Lights are only for Fish Only marine tanks or Freshwater low light planted tanks (crypts, anubis, java fern etc)"
 
Sooo by the marineland's website information I'm very very low on light to grow anything? Or am I wrong? Panicking of course that all my plants will die.....
 
Need advice to add more lamps or not. Marineland is very affordable but i'm not expert in quality of theirs product...

 

[Byron]

Can you post a link to data on the light you have?  I would agree that it sounds like insufficient, and if you can, it would probably be best to exchange it.  You want light that has some red in the spectrum, this is essential for photosynthesis, along with blue, but green too will improve the colour aspect.

 

[RinaLane]

Here is my lamp http/www.petmountain.com/product/aquarium-led-light-fixtures/11442-524764/marineland-size-48-12-watts-aquariums-48-60-wide-.html Here is their official web-site with negative review only http/www.marineland.com/Products/aquarium-lighting/LED-Aquarium-Lighting/LED-Strip-Light.aspx

I was thinking maybe if I buy 2 more of same kind led strips in total i'll get 2106 lumens will it help? Because by the size of 1 have I can fit in only 3 of those on my glass top...
Any other suggestions for good & unexpensive led strips for glass top?
I dont plan to have forest or carpet just disent ammout

 

[RinaLane]

I'm not planing to cover every single inch of aquarium's floor with plants just back wall with something long to create 'bushes' and lots of swords + anubias up front to make it look green & not plain empty.
 
 
 
I appreciate any help with lightning

 

[Byron]

The fixture linked is the "Single Bright" and that will not be sufficient for much beyond moss.  I was looking into the "Double Bright" when my T8 fixture gave out last year, but I felt even that was not sufficient.  I ended up going with a brighter LED that was said to be equivalent to two T8 tubes (which is what I had before) and I bought it, but after two weeks I managed to sell it although at a loss, but it was no where near sufficient, plus it was too blue.  The fish looked weird.  And I only have low and moderate light plants such as what you're intending.
 
Adding more fixtures is not the best way to go, as they take up space and while that may not seem much of a problem, once you start doing regular maintenance and feeding, it becomes a real pain having to move the lights off the tank.
 
If you stay with LED, I would look at much brighter fixtures.  Some of them really are designed for planted tanks and have red, blue and white LED bulbs, and these are the best.  Beyond my disastrous experience I can't say much more on LED, only that it is possible but you need to get the right fixture.  They are expensive, though supposedly make up for this in lower operating costs.  But they do give out, and then need to be replaced.
 
Byron.

 

[RinaLane]

I looked for T5s http/www.petmountain.com/product/aquarium-fluorescent-light-fixtures/11442-585266/coralife-coralife-aqualight-t5-dual-fluorescent-lamp-fixture-freshwater-aquariums.html Is this one warms the glass & the water & gives lots of side light?
 
Also if length of my aquarium is 48,25 (122cm56mm) & I buy lamp 48 inch long.... Can it stand on my top or its too big? On pictures looks like 'legs' need at least 2 more inches on each side ><

 

[Byron]

I looked for T5s http/www.petmountain.com/product/aquarium-fluorescent-light-fixtures/11442-585266/coralife-coralife-aqualight-t5-dual-fluorescent-lamp-fixture-freshwater-aquariums.html Is this one warms the glass & the water & gives lots of side light?
 
Also if length of my aquarium is 48,25 (122cm56mm) & I buy lamp 48 inch long.... Can it stand on my top or its too big? On pictures looks like 'legs' need at least 2 more inches on each side ><

 
Now we are going in the opposite direction...a T5 with two tubes will be way too bright and you will have algae soup.
 
A short explanation, if I may.  The "basic" fluorescent tubes were originally T12, and over the past several years these are being phased out and replaced by T8 which are more efficient.  But these are the basic fluorescent.  And the "T" number is simply the diameter of the tube in eighths of an inch, so T8 is 8/8 or 1 inch diameter, and so forth.  T5 as far as the hobby is concerned was developed primarily for the marine side.  The output is roughly one and a half times more intense than the same length/spectrum in T8.  So two T5 tubes produce light intensity roughly the same as three T8.  The advantage here for marine tanks is that they need more light for corals, and with T5 you have fewer tubes to achieve it.
 
I tried a dual-tube T5 over my five-foot 115g (the one that developed the broken T8 fixture) and after a week I realized it was way too bright so I returned it.  That was when I tried the LED I mentioned previously.  After that fiasco, I decided to make my own--a risk, as I am not very mechanically-minded, but it worked.  I found a T8 dual-tube shop light at Home Depot that fit nicely into the housing I had.
 
Your 75g tank is four-feet in length, and a 4-foot fluorescent will work fine.  I have this over my 70g and 90g which are both four feet.  I have two T8 tubes.  I have been using this light for 20 years, so I understand it and it works perfectly for my purposes (moderate light planted tanks).  Fixtures in T8 are very hard to find now, having been supplanted by T5 and more recently LED.  If you could find a single-tube T5, that would be an option.
 
As for how that fixture sits on the tank, the ends of a 4-foot fixture would sit on the tank frame.  The wire extensions are for longer tanks (like my five-foot).  You must have a glass cover on the tank though, so water will not splash onto the tubes, and condensation too.  Plus some fish jump, and might burn on the tubes.  This glass cover would be needed for most fixtures, though some LED might have covers of their own.
 
Byron.

 

[RinaLane]

But will t5s add extra heat to the water? And thank you again for your amazing answer

 

[Byron]

But will t5s add extra heat to the water? And thank you again for your amazing answer

 
You're very welcome; I only hope all my blabbing actually helps some.
 
I don't remember the T5 I tried for a week being any more heat than my T8's.  Yes, there is heat, but this is not that significant, plus it is natural as the surface of tropical waters is always warmer.
 
There is actually a considerable temperature gradation in most aquaria, certainly in mine.  When I stick my hand in during water changes to re-arrange wood or plants on the substrate I am often surprised by how cold it is compared to the surface.  I'm not talking 10 degrees or anything, but it is obvious.
 
Byron.

 

[RinaLane]

Thank you I think I'll go withT5s then. They seems more reasonable for price & what amount of light I'll get. Also I think I won't have to threw away whole lamp when 1 of T5s will break like it would happen with my Led one isn't it?

 

[Byron]

Thank you

I think I'll go withT5s then. They seems more reasonable for price & what amount of light I'll get. Also I think I won't have to threw away whole lamp when 1 of T5s will break like it would happen with my Led one isn't it?

 
Careful...a dual T5 is way more light than you will want, unless you intend going full high-tech with CO2 diffusion and daily fertilization.  If you can find a single-tube T5 fixture, that would be good, but not two tubes believe me.  There were a couple of threads not long ago where algae issues were a real issue, and it came down to the T5 lighting.