questions about lighting

yyankeeyankeefan

i have a 60 gallon tank. about 24 inches high, 15 wide and 48 long. i am having a hard time putting lights in there. it takes two 18 inch bulbs. t8. what should i use. the largest watt i can find is 15, and how much specturm should i have. i can find a bulb as high as 800k but that together would be 1600k. kind of a lot...over kill and create aglae growth or go for it?

Geomancer

Well, the solution is simple =)

I'm guessing you mean 8000K? That's the color spectrum, and the K stands for Kelvin. It's just a measure of what wavelengths the light makes, plants need a specific wavelength of red and blue to grow. The ideal number is 6500K but anything between 5000-7000K is useable. This color temperature is not cumulative, so two lights at the same color temperature would not be 2x the number.

It's wattage that is cumulative, as with more lights you'll have more energy hitting the plants leaves. Wattage for fluorescent tubes is pretty much fixed, you won't really find variation like you do with house bulbs. Just go to a hardware store and look for Daylight bulbs, all the big guys make them (GE, Phillips, Sylvania) and they are usually 6500K.

Byron

I concur with geomancer, but will expand a bit.

First question is, what sort of plants do you want to grow? Plants need light, but there are roughly three levels in this, what we term low light plants, moderate light and high light. The fixture you now have is only going to cover low light and some moderate light plants.

Fluorescent tubes come in various lengths to fit the fixture, and all tubes in a certain length will be the same wattage, basically. Some manufacturers now make more energy-efficient tubes, so the wattage is lower. Watts is only the measurement of the amount of energy it takes for the tube to light. The intensity of the light it produces is determined by the phosphors inside the tube, and these also determine the colour (measured in Kelvin). Most 18-inch tubes will be roughly the same in light, depending upon the type. Some are better than others and produce more intense light.

So you have two options. Staying with the present fixture, buy two good tubes to provide the best light possible with this arrangement. Or, replace the present fixture with one that takes 48-inch tubes.

Staying with the present fixture, I would recommend two tubes. The Hagen Life-Glo is one, and the ZooMed Ultra Sun is the other. These both have a Kelvin of 6700K (the ZooMed might be 6500K, much the same) and provide good clean light. With these you can have low light plants (Anubias, crypts, Java Fern, Java Moss) and some moderate light plants like green-leaf swords, Pygmy chain sword, Brazilian Pennywort, and floating plants like Water Sprite.

Hope this helps.

Byron.

yyankeeyankeefan

thank you. i am going for low light plants atm because i can't afford to upgrade the lights right now. eventually i want to get the tank so i can do all moderate plants. i currently have a tropic sun (made by zoo med) one one side (my other tropic sun light blew out and had to return it) and just the standard one that came with the hood in the other.

Byron

The one that came with it will be less intense, so I would replace it. I mentioned the two that would do best for you, of those I myself would go with Life-Glo, though a tad more expensive. Both tubes should be the same for appearance.

yyankeeyankeefan

i am going to replace them (i hope) next week :)