I have a new 75 gallon tank and am still getting equipment before I set it up in a week or so. should I get use 1 300 watt heater or 2 200w heaters on opposite ends of the tank. Also which brand. Eheim or Fluval
Dual heaters is a common recommendation in case one fails. The difference in 300 Watts vs 400 Watts would be best answered by how cold is the coldest the room gets, and what's your target temperature? If your room is within 10 degrees of your target temperature at the coldest, 300 Watts is plenty, if your room gets down 15 degrees below, try 400. In really cold rooms you could go up to 600 Watts total in a 75.
I can't say I have ever compared those two brands heaters in my tanks to I can't give you any input on that. Both are great brands, if go with the one you think looks best or is the easiest in your opinion to adjust.
I try to maintain 78 degrees in the tank. my house gets down to mid 60s when the wife and I are at work. but we keep house around 68 when we are home. I bought 2 200 ehiems. the 300w is too tall for the tank and I don't know how I feel about using it horizontally
Here is the table to help with what size individual heater you need. Delta T is the difference from the lowest ambient room temperature in the room to your desired tank temperature. Always get a heater larger than you think you need so just round up to the next nearest size.