Teklights don't have waterproof endcaps. Keep an eye on them with splashing fish around.

I'm an electrician and my best advice to you is not to change 1 bulb at a time, change all the bulbs on a ballast. If you have 2 ballasts with 2 bulbs burn out... Change both on that ballast not just the one. By changing one bulb only you are reducing the life of the ballast and both bulbs due to harmonics, applies to electronic and magnetic ballasts. Something else to consider is one of the greatest advantages of t5 is there effiency. A t5 bulb will only lose on average 5% of its effiency when it finally burns out. Changing a t5 every year is like flushing money down the drain. Mine are 3 years old now, measured with a par meter from work about 7 months ago and I had only lost between 1% and 6% across the 4 bulbs I have.

Funny, Ive seen lots of posts with PAR readings saying the opposite.


I gotta buy a PAR meter and test myself I guess

Ya for sure, all information should be taken with a grain of salt. I tend to agree with an industry that is responsible for installing hundreds of thousands of t5 fixtures over an extremely small industry serving the needs of hobbyists ;) I also do not buy $30 bulbs from germany for the most part, no choice for actinics, I can buy a case of 40 bulbs for the cost of 4 'reef' bulbs. Again I'd trust the quality of companies like sylvania and ge making millions of these over some rebranded bulb. Kelvin rating is changed by the phosphor coating on the inside of the bulb... Is that worth 10 times the price and supposedly far far less effiency? Ill stick to my $3 10k bulbs that seem to work as effiently as was intended for T5. The way this hobby industry portrays T5 negates almost all of the benefits of T5, I'm guessing to sell more bulbs. Again grain of salt ;)

I thought the colour temperature changed over time as well on fluorescents, not just the loss of efficiency?

If it changes its slight, basically electrons bouncing around in the glass tube interact with the coating on the bulb, the phosphor coating doesn't break down all that much, its the vapour inside the tube that breaks down, causing the effiency to decrease.

So, Binare, what brand and model of T5 do you use?

I use workhorse ballasts along with GE 10k bulbs.

The GE bulbs are rated at 25,000 hours lifespan. and are 95% efficient at 40% of there lifespan.

I run my lamps 10 hours a day, which works out to a 2500 day life span (average) or almost 7 years. Take into effect the efficiency (95%@40%) and I change em roughly every 3 years or so.

They cost me about 3-4 bucks a piece. 17 bucks per ballast.

4 x 39W on a 12g?

That is correct