Setting Up A 'Temperate' Pond

Pond holds 300 litres of water approx. ( including filter). It’s rectangular (950 x 550 x 575) actual internal dimension.
I am going to push up the temperature to 22 C and modify the heating to include another temperature controller as a ‘failsafe’. I have found that 1 of the 300 W heaters is perfectly capable of heating and maintaining the temperature even during the recent cold spells. I can run one of the controllers at the same temperature setting (22 C) with a slightly increased heating / cooling differential (say 1.5 C). If the main heating circuit fails the backup will take over.
I can change them round occasionally to allow each heating circuit to operate.

I had stopped for a coffee after cleaning the tank that contains my rainbow shiners, and watching your gang in your pond made me chuckle with joy. They all look so perky, and with great colours. Your plants look lovely too.
Well done. 

Temperature is now set to 24 C. A bit of Sun on the pond yesterday and the temperature crept up to 25.1 C (red warning on the graph). I had the high temperature warning limit set to 25 C so I set it to 26 C to cater for the increase.
I might have to get the fan out sooner than I thought.

Hi @daveyng great to see more of your pond! 

Here's the latest on the Pond which is now in it's fourth year.
Current inhabitants are mainly Barbs (Golden, 5 Banded and Odessa) with some Diamond Tetras, White Clouds  ,Swordtails and a few male Endlers. There are also a few Rainbow Shiner left from my original shoal.
There are also Amano shrimp and Cherry shrimp as well.
I keep the pond covered in Winter and place a fine plastic mesh over it during the Summer which keeps the temperature down to a reasonable level. Currently the average temperature is around 24 C.
I have 2 x 300 W Titanium Heaters on Separate controllers in case of failure.
The Pond is monitored with a Seneye device.
I have attached a few pictures from a video I produced recently(I'll add a link to that soon).

Have to remember how I added the videos. I’ll try again later.

One thing I have noticed is the difference in behaviour of the fish in the pond in comparison to aquarium residents. They tend to be more ‘lively’ and aware of their environment than their indoor counterparts.
They seem to grow more rapidly and their colours are more intense.
Probably due to the extra live food (insects etc.) they have available to them.

Have to remember how I added the videos. I’ll try again later.

I usually find inserting a third / after the https: sorts out the problem (think @Robert advised that long ago), but glad you've somehow managed to upload it.

Great to read of the pond updates and to see how lively the fish are - wow!     
How do the titanium heaters work ie do you have a power supply somehow connected?
I imagine the extra space in the pond (.v. an aquarium) likely helps the fishes' growth.  I once spotted an x-ray tetra in a LFS which was a lot larger than any of mine ever reached - I suspect it had lived in a comparatively large tank but had been brought into the LFS for rehoming.
Thanks for sharing the video and the 'stills'. 

Your gang are very active in the video. Great to see them all doing so well. 

Thanks for the pics and update on your pond.
Great to know that everything is going well and looking good.