How to tell which *old* lights will grow plants and which won't

[earhtmother]

I only have *used* tanks which ofcourse means *used* lights, some T8s, a couple of T5s. I will be replacing them as I can afford to but for now I have to make do with what I have. My question is how do I tell by *reading* the bulb if it will grow even low light plants? I also have some newer LEDs which I *assume* I should be able to look up online.

 

[Leeatl]

See if you can find the K value of the bulbs...6500K is good for most plants and the leds should be ok for plants too .

 

[King Fisher]

You can grow low light plants with almost any light if the tank is 24 inches or less.

 

[libertybelle]

You can check the wattage of the old fluorescents and get a ballpark idea by determining watts per gallon

 

[earhtmother]

Liberty
What amount of wattage am I aiming for??

 

[libertybelle]

That depends on what you want to grow.

I read something like 1-2 for low 3-4 for medium and 5+ for high. Just remember this comes with massive caveats. Depth of the tank and color of the light makes a huge difference( honestly making the ‘rule’ almost useless.)

This ‘rule’ is about as useful as the inches per gallon rule. It can give you a general idea but it can also lead you astray. Better bet is to tell people on here all the info you have on the setup (tank dimensions, wattage, color and type of bulb, lumens etc) and maybe someone on here can help you decide. Remember If you’re not dosing fertilizers or running co2 you may find you want to limit light to avoid algae overgrowth.

 

[Coursair]

A PAR meter will tell you how much light is reaching the bottom if the tank has water in it.

A LUXE meter will read dry lights I believe ?? Just adjust distance to read where bottom of tank would be.

If the bulbs are old, swap them out, I try to swap my T5HOs out at least yearly.

You can buy LED T5 equivalent bulbs...but no idea how they’d work on aquatic plants.

I’m very pleased with some of the new cheap LED panels in my Carnivorous Plant greenhouses

 

[Coursair]

One of my Nepenthes under LED panel just to show some of the new LEDs are getting quite good.

 

[Caliban07]

All visible light will grow plants. You don’t even need strong lights. Just pick a colour temperature that pleases you aesthetically and your good.

 

[Delapool]

All good points above.

My first light was some used light and bulb. Tank was foot and half deep. Fine-leaf stem and floating plants did pretty well and I can’t remember changing the bulb for several years as never knew about that.

Give it a try. From PAR measurements and swapping to new bulbs, I think there is some fade and maybe small spectrum shift but hardy plants near light might not care. For high tech tanks I think I worked out that replacing the bulbs every nine months or so was worthwhile (was on fine balance between little algae and getting algae so more about stability for me plus deep tank).