Confused by heating options

[StarJohn]

Hello fellow hermie owners
I have had my two crabs now for just over four months. For the first three months (being an Australian summer) I was able to maintain optimum temperature and humidity without much variance. Now that the weather is cooler obviously heating has come into play. For the last few weeks I have been using a heat pad (15x28cm 7watt in a 25gallon tank). It is mounted to one half of the backwall two thirds of it under the substrate and one third above and plugged into a thermostat. Admittedly both the pad and the thermostat are relatively cheap ones. I am finding the temperature is swinging considerably. The temperature is staying between 74°F and 80°F during the day but drops a lot at night and in the early morning to 70°F and sometimes as Low as 65°F. And these temps are at the hot end! perhaps I am not using a powerful enough heat pad???? I am considering two options but am quite confused as to the best course of action.
1/ mounting a second heat pad at right angles to the first at one end of the tank. I think this would be the simplest option for me..
2/ using a CHE. Although based on my research I am confused about how to do this. What wattage? How do I mount it? I have a glass lid.
I know there is a lot of information on this website as well as others about this topic however there are so many different options and opinions that I am a little confused about what is best to do! I am so new to the heating thing and really didn't know what I am doing!! Any help and advice would be very greatly appreciated.

[emmac350]

Is your thermostat probe in your substrate? What temperature do you have your thermostat set to? The temperature you're measuring that has you concerned - is that the air temperature or the substrate temperature?

If your heat pad is mostly heating your substrate you should have your probe in the substrate in front of that pad, but not touching it. For added help keeping your tank warm you can surround the substrate with aluminum foil, shiny side toward the tank. At that point you shouldn't need to worry as much about the variation in the air temperature because if the crabs are too cold in the air they can bury into the warmer substrate. Test the temperature in your substrate with a meat thermometer or something similar to see what it is in several areas near and away from your heating pad before you decide it is or is not enough for your tank.

A Ceramic Heat Emitter might be required given your situation if you can find a good tank hood, but this will mostly raise your air temperature and quite radically. With my CHE on it's not unusual to see air temps in the 80s and for those temps to slowly lower when it turns off into the 70s.

[StarJohn]

Thanks Emmac350. I don't currently have my thermostat probe in the substrate. It's at the warm end of the tank suspended about 3/4 of the way down. I will definitely take your advice and get a meat thermometer to check the substrate temperature though. When using the foil as you suggest should I cover the heating pad or leave that uncovered by the foil?? In the cooler times of the day my Hermes are butting themselves up against the glass where the heating pad is

[appps]

When we got our last crab he came with a small tank with UTH heaters that I kept him in for quarantine. I found the same as you coped during the day but was dropping heaps at night, and it wasn't even winter!

That little tank had two uth on it too! One really would have struggled. One on the back and one on the side.

I ended up getting some cardboard which I put round and over the top at night to help insulate it better. (The heaters also already had polystyrene on the outside of them to divert the heat back inside) It's a bit like our house windows I figured, we wouldn't have them without curtains at night because we would loose too much heat through the glass. It didn't bother me to insulate him at night as it also gave him some night time as he was near our kitchen so got light till quite late otherwise.

Just want to add a disclaimer. I wasn't sure about the polystyrene so googled. Some brands come with recommendations that it is safe to use, some don't. It made a big difference to the efficiency of the heater but make sure yours is a heater that says it's safe to use with before adding. You don't want to melt it or worse. The cardboard was only added to the non heater sides.

[emmac350]

When using the foil as you suggest should I cover the heating pad or leave that uncovered by the foil?? In the cooler times of the day my Hermes are butting themselves up against the glass where the heating pad is

I cover the heating pad too; I figure that the pad itself will radiate heat in all directions (less going away from the tank, but it still *feels* warm, so that is losing heat) and I want it all to go into the tank. The foil going over the pad will warm up all the rest of the foil, which will help at least a little to spread that warmth throughout that metal. And it is safe to do - there's a reason we use foil in our ovens - it's safe to well over 400F/200C and I promise your heating pad won't get that hot.

Edit: I moved this to the weather forum as opposed to the water one, since the conversation is about heating.

[StarJohn]

Thank you so much Emmac350 and Appps! Great advice I will be using for sure. I have just purchased a more powerful UTH online as well. So fingers crossed I can get the heat stable!
Thanks for moving the post to the weather page Emmac350. That is where I thought I had put it and I couldn't work out where it was when I went back into whether to look for it.
I can't tell you how fantastic this online support is. I would be lost without it!!!

[emmac350]

No problem - always wanting to help people out with their crabbies. Besides, if we don't help out here, why would people come back for assistance?

Let us know how the new heating pad works out...hopefully everything will get stable!