The Planted Tank Forum banner

Lighting

649 views 4 replies 3 participants last post by  Taari 
#1 ·
I have two T12 light fixtures. The label on the fixtures says 48x18 120v 40 watts. Each one holds two 20 watt bulbs. I want start growing plants. My tank is a 70 gallon high. The cover is glass. The distance from the gravel to the light is approx. 20 inches. I know this isn't enough light to grow plants. Can I replace the T12s with T8s? Would this give me more light than the T12s?


This is my first post. Love this forum!
 
#2 ·
You can retrofit your current light fixture, but to change the bulbs, you for sure have to change the ballast, and you might also have to change the end caps. They do make ballasts that will run both T12 and T8 bulbs, but you probably don't have one in your fixture.

That said, even two T8 bulbs probably wouldn't be enough light for a 75 gallon tank to grow plants. A better option would be a fixture with the option to run 1 or 2 T5 High Output (HO) bulbs. One bulb will give you enough light to grow a fair number of plants, and two will give you even more options, depending on how efficient the reflector behind the bulbs is.

A quick guide to reflectors is this:

If you can see multiple reflections of the bulb on either side of it, you have a very good reflector.

If you can see one reflection on each side, you have a good reflector.

If you can see a partial reflection on each side, you have a fair reflector.

if you can barely see any reflection or no reflection, you have a poor reflector.

Just be sure to research about planted tanks if that's the direction you are going. Lighting is only one aspect of having healthy plants. You also need to consider nutrients, including CO2.
 
#3 ·
Maybe my post was confusing. :confused:I have two fixtures on my tank with a total of four bulbs. Each fixture is 48 inches long with two 20 watt bulbs in each. So if I were to change the ballast to T8s and have four 20 watt T8 bulbs, would it be more light than 4 20 watt F12 bulbs?

Thanks for your help. I'm an experienced fish keeper. Not so much with plants though. I even had a salt water reef for a few years. I'm making MTS for the base. I'm not sure what I want to cap it with yet.


What do you mean by
"If you can see multiple reflections of the bulb on either side of it"? On either side of the reflector? The water?

Thanks Taari
 
#5 ·
Ah, if you have 4 bulbs and changed the ballast then 4 T8's would be enough for low light plants.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top