on my 125 i have a Marineland Visi-Therm Heaters rated for 125 but my temp is steady at 73.6 i need it to be at 78 what should i do add another heater?
I have a 75G with a 30G sump being heated up by two 150W heaters. I set them up to 82 deg but have them hooked up to my controller. My temp has been consistently between 78-79F.
Just to reiterate, I have the heaters monitored by the controller and I DON'T rely on temp setting on the heater itself.
I have 2 200 wt heaters on my 120, so if one goes bad at least I have one left to do the job. There was a recall on the Marineland stealth heaters. (KathyCs sticky post). I returned mine last week for a refund. My Marineland Visitherm which I use for my s/w mixing just crapped out yesterday. If you get another heater I would stay away from any Marineland heater.
I went through a lot of heaters. I am currently running a Blueline Biotherm Titanium heater. Be carefull with titanium heaters. All they are is a glass heater in a titanium sleeve sealed by rubber plugs and depending on the brand, sealant is also used.
I would buy either an oversized heater, used on a controller, or 2 smaller sized used on a controller.
heaters are rated to keep temp so many degrees above ambient room temp, which they probably rate at 72 deg room temp. so if you have a cold room you will need another heater. you should run 2 anyway. they say 3 watts per gallon minimum, so your right at the min.
The Eheim - Jager heaters are excellent.
Your best off putting 2 heaters in the tank for redundancy. 2 x 200W heaters should work fine in your set up.
If one stops working your temp won't drop that low and if either overheat, your temp won't get stupidly high. All heaters should be run off a controller ( I see you are alrready doing that though!)