I have a visa therm 25 or 50 watt in mine. they are both 9" long.

 

skinny and short only 6 1/2" long

have one on my 2 gal and going to get another soon for my 10 gallon.

 

The Cobalt neo-therm all the way. Its a solid heater. Only need the 25 watt for the spec v. It fits perfectly in the chamber with the pump.

Amazon.com : Cobalt Aquatics Neo-Therm 50-Watt with Plastic LED : Aquarium Heaters : Pet Supplies

skinny and short only 6 1/2" long

have one on my 2 gal and going to get another soon for my 10 gallon.

 

Read the reviews for the Spec 5 on Amazon. Most people there describe the add on stuff that they use.

 

Thanks for the help poeple. I like the look of that cobalt I think I'll give it a try. The last visatherm almost electrocuted me Be careful with those things. I bought one new and put it in my tank. I stuck my hand in the tank and got zapped pretty good from it. I've always liked the brand but the new ones are junk.

 

I use this in my Spec V. Probably should have gotten a higher "W" but the room it's in stays pretty warm anyway. I love how this one has a light to tell me if it's on or not too
Amazon.com : Hydor 25W Submersible Aquarium Heater - Original Theo : Pet Supplies

 

Either the Hydor 25W or 50W will fit right inside the outflow compartment. Amazon has them at great prices and they're well rated.

 

Amazon.com : ViaAqua Titanium Aquarium Heater, 50-Watt : Viaqua Heater : Pet Supplies

 

^^ +2 to the Cobalt NeoTherm. There have been issues with the big ones (100w+), but the smaller ones (50w and under) have been solid. Fit fine in the pump compartment.

You can see the top of it in my Spec V here: