How much Light is enough

[YukonCaper]

I just purchased a T5 light for my Low tech planted tank. I am still in the process of cycling it, so I have no plants in it yet. I do have eco complete gravel in it and have some plant tabs to place once I am ready to bring in the plants.

My question is, how much light will this 20gallon tank need? I was thinking to put it on a timer so it gets the optimal amount of light, but what exactly is that? Any suggestions or comments welcome.

[Zefrik]

It depends on how many watts the bulb is running.

[YukonCaper]

Hmm, good point. I will post back once I pull everything out of the box and do a bit more research on what I have. Thanks

[Robert H]

You need to find out if its a T5 NO or T5 HO. HO gives you a ton more light.

[kamikazi]

It also depends on what you mean by low tech. Are you doing DIY Co2 or dosing Excel, some people consider those methods "low tech"

If its a T5 HO light and you aren't planning on injecting any CO2 or dosing Excel you will need to raise the light to an appropriate high so as not create a great habitat for algae growth. Check out this thread for a very helpful chart. http://www.plantedtank.net/forums/li...t5-t12-pc.html

[YukonCaper]

I am not injecting CO2, but I am dosing with a liquid (leaf Zone). I have eco-complete substrait as well, and the plant tablets under the substrait. I sure hope i can find success without having to go the route of getting a CO2 system.

The light is in fact a T5 HO. At the moment I have a number of plants I purchased off a fellow enthusiast in the tank. The light sits on the top of the tank and is not elevated above the glass cover.

I really want to make this work, so any help is appreciated. The light is on a timer and I have it set to come on at 7 am until noon, back on at 3pm and then off again at 11pm. I am not sure if this is optimal.

Oh and another question, does adding aquarium salt to the tank adversly affect the plants? I am looking at getting some mollies which like a bit of salt. I wont do it if the salt with hinder the plants though.

[Diana]

Do not add salt. The plants do not like it.
For Mollies, hard water (GH and KH over 10 German degrees) is OK, salt is optional.
I would not put Mollies in a 20 gallon, though. They can get quite pushy with each other.

[Hoppy]

Any T5HO light that sits on top of a 20 gallon tank will be too much light for a "low tech" tank. Even 2 bulb T5NO lights will likely be too much for a 20 long tank. You can't compensate for the high light intensity by just running the lights for a shorter period. Light isn't cumulative to much of a degree.

[YukonCaper]

Originally Posted by Hoppy

Any T5HO light that sits on top of a 20 gallon tank will be too much light for a "low tech" tank. Even 2 bulb T5NO lights will likely be too much for a 20 long tank. You can't compensate for the high light intensity by just running the lights for a shorter period. Light isn't cumulative to much of a degree.

Thx Hoppy. The T5 light came with a couple of brackets that can be used to raise the light up and away from the tank a bit. Do you think using them will lower the intensity a bit? What signs will I see if the plants are getting too much light? What should I watch for? I am all ears.

Thanks in advance.

[Hoppy]

The plants will do fine even with "too much" light, if you use CO2 and fertilize well. But, algae will very likely do much better, especially black brush algae. If the plants are well supplied with nutrients, they will grow much too fast with high light. This can force you to do twice a week pruning just to keep up with the growth, and one day the tank will look perfect, but the next day it will start looking overgrown. People who want a planted tank to enjoy, not to be a slave to, tend to want much less than high light.

Raising any light will reduce the intensity. But, I don't think a 3 inch raise will be enough to make a big enough difference. You can suspend the lights over the tank by one of several methods, and reduce the intensity enough that way, but you may get a lot of light spill onto the floor and back wall that way.

[exv152]

What's the total wattage you're running with that fixture?

[YukonCaper]

Originally Posted by exv152

What's the total wattage you're running with that fixture?

Admittedly, I am not yet sure what wattage. It is a hagen GLO T5 HO light with a single tube. http://www.hagen.com/pdf/aquatic/GLO...Program-EN.pdf

I will look closely at the box when I get home tonight. I am guessing however that it is a 24W light.

[Hoppy]

A one bulb Hagen Glo light might work fairly well for low medium light if you use the "feet" it comes with. Those lights don't have the greatest reflectors, and with just one bulb instead of the usual two, you get less light too. I'm assuming you have a 20 gallon high tank, about 24 inches long and about 16 inches high. If it is a 20 gallon long tank, it is only about 12 inches high, so even with the legs it will be way too much light. To make that work you could use 2 layers of Home Depot fiberglass window screen (insect screen) between the light and the tank, which would drop the intensity down to the low level needed for a "low tech" tank.

[Miles]

T5's on a 20 are pretty intense, I had 2 22" t5's on a 20 long, tonnnssss of light. Everything grew like crazy, unfortunately that included algae, I'd shoot for around an 8 hour photo period.

[macgregore]

it is very important to realise that the success of a PLanted tank, any tank is a reproduction of a natural ecosystem that needs light/co2/fertilization.

i guess what you are doing here, is trying to bypass the injection of CO2 and adding all ingredients to a successful tank. What is bound to happen is that it will be out of balance. the over lighting of the tank should be counteracted, which is obvious. and it is usually counteracted by CO2 addition or decrease. Now adding fertilizers like leaf zone has its problems too. Leaf zone is extremely rich as you should be aware. what can happen is that the moment the dosage is not fully absorbed by your plants; it will couple with the light and bring to the tank algae. only then nature will find its balance, but not giving you the ideal look.
Leaf zone could as well, if the prescribed dosage is applied to your tank, turn the water yellowish. I am sure that many out here will agree that without this balance of Light/CO2, planted tanks can prove to be very messy and far from what you aspire.
My experience also showed me that without CO2 and well lit aquarium; upon regular and very regular water changes and very limited fertilizer dosage; you will notice that the plants will reach very quickly a point of saturation. - minor improvements in growth, minor reproduction and sometimes no reproduction at all. the percentage of CO2 in air is much higher than that in Water, and you will have to wait for the CO2 in air to diffuse in the water to for your plants to absorb and this rarely starts any pearling of your plants.
i would suggest you, since you made some expenses already to get a successful planted tank; make a slight effort to include any means of CO2 injection( DIY or Pressurized). you will be praised for this effort.
i will certainly not create precedence saying that it will not happen at all without CO2, but i guess that you are not experimenting with this tank and want to enjoy a nice scape asap and start up a bigger one like most of us. A low tech without CO2 tank is maintained differently and is not the best of all. hope it helps and keep writing