Lighting overheating tank?

I looked for a place to post my question but couldn't find one. I'm sorry if this is in the wrong spot. I looked for an answer on the different forums but didn't find one.

I have a 70G tank. I put some live plants in it. I wasn't sure what type of bulb was in the hood so I replaced the light that was on the tank with a T8-32W-8000k-full spectrum bulb. It is a single strip lighting fixture.

Now the tanks seems to be heating up. In the last week, the temperature has gone from 76 to 84. The temperature in the room the tank is in is at 76 today, but that's the warmest it's been all week. It has been 73 in here. I thought the light might heating up the glass top so yesterday I raised up the light about an inch. It was still high this morning so I put the light on 2 upside down loaf pans and unplugged the thermometer. I also dropped a water bottle with about an inch of frozen water into the top of the tank.

Did I get the wrong size light fixture? Is it just down too low? I'm afraid if I raise it up any higher, it won't do the plants any good and they are doing great now. I have a hornwort, an anubias, amazon sword with 3 runners, jade and I think baby tears. When I raised the light up higher, it created shadows in the corner where the hornwort and baby tears are.

The fish in the tank right now are 9 Zebra danios, 6 neon tetras, 5 panda corys, and 2 swordtails (I had gotten 1 male and 2 females but one of the females wasn't good when I got them and she died). I want to get some more pandas, another swordtail and some other fish, but I don't want to do it until I get this temperature thing straightened out.

 

Your question has been moved to a thread of its own to have a better chance of getting feedback.

Lights do generate heat which in turn can warm up the tank. Instead of raising your light I would look at ways to help reduce heat, including:

Add extra airlines to create more surface disturbance
Leave the lights off during the warmer part of the day
Maybe even running lights in the evening only
Turn down the heater
Open the glass top if your fish won't jump out
Point a fan at the tank to help dissipate the heat generated by the lights

Good luck.

 

Thank you for your quick response. I usually turn the light on when I get home from work in the morning and turn it off when I get up at night. I leave it on all day for the plants. I wouldn't want to leave it on all night because then the corys would never have any peace. I will have to do some more research on my fish to see if they are jumpers. I have unplugged the heater for now. And I will point a fan that way to see if it helps any.

 

Get yourself a timer and run the lights about 8 hours. Leaving it on so long is adding to the heat buildup and may lead to algae down the road.

 

That's an excellent idea! I will get one when I get paid this week. And I am going to have my husband fit a screen on at least one side of the top so I don't have to have the glass all the way across the top.

 

Great advise from catsma

Where is your thermometer placed and what sort? i.e. glass "in-water" or digital "stick-on". Is at the top or bottom of the tank. Is the temperature even through out the tank.

I know lights can heat a tank, but I wouldn't have thought it would heat the entire 70G, but I could be wrong, T8s do run hotter than T5s.

Also, be prepared that removing the glass top may result in higher evaporation

 

There is a stick-on thermometer in the bottom left of the tank that reads about 82 and a floating thermometer stuck with a suction cup to the upper right. It now reads about 80. Should I maybe get a T5? Would it give my plants the same benefits as the one I'm using now? It's funny (not really) because when I went to buy a light last week, I first picked up a T5 bulb at Walmart but wasn't 100% sure it was right. So I stopped at PetSmart and they sold me the T8. I probably should have known better. It also cost me about $10 more than the Wallyworld one.