Nice to see this tank, brings back memories for me as I had exactly the same tank, 3 foot ClearSeal tank.
It’s actually a really good bare tank to start with and lots of options for this.
First, I used a Fluval C3 hang on back filter that worked really well, I put this on the side of the tank, fits nicely and you can adjust flow to suit and I filled it with my choice of media and filter floss which I changed every week (the floss not the sponge or bio media) to help clean the water column.
Took screenshot from eBay just to show you which filter I speak of, a little pricey but worth it.
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Of course does not need to be Fluval or even a hang on back filter, just a suggestion to let you know what I used
For heating I had a Fluval E series heater, very easy to adjust heating and also on the LCD it lights green on display for normal heat, blue for too cold and red when too warm so easy to see readings on that so that gave lots of peace of mind, a bit more pricey for that but I got that one free anyway due to a offer from Amazon luckily but really do recommend that though.
But I did have another ClearSeal tank and as it happens I did have a AquaEl flat black heater as you showed in earlier post, fairly easy to adjust heating as its a dial type adjustment thing so that was perfect for that tank as I had a black background on rear tank glass so it kinds of blends in the heater but my plants hid the heater eventually anyway!
Two recommended choices there!
Light was a over tank unit with 2x T8 tube lights, great lights but now you can get much more energy efficient LED lights that will do just as good if not better at plant growths.
As for stocking, I too had fairly hard water, and I had threadfin rainbow fish in the smaller ClearSeal tank, lovely fish to observe especially the males flaring their fins.
The 3 foot had, despite having hard water from tap at ph of 8.0 but in this tank the ph was around 7.2-7.5 due to substrate, lots of bogwood and lots of plants and the stocking consisted of CPD, Lambchop rasboras (Trigonostigma espei), black bar endlers and a whiptail catfish (Rineloricaria sp.), Amano shrimps, Red Cherry Shrimps and loads of MTS snails.
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Lovely tank that was.
(Closed it down and sold tank, light, plants and equip as job lot for a very good price due to moving house)
Oh just remembered, you mentioned adding Perspex for tank cover, not a bad idea but at 3mm, I’ve tried that on a different tank as a lid cover and it eventually bends upwards at edges due to heat of tank and lights etc, even with holes into it to let oxygen exchange take place. Would try thicker Perspex at least 6mm, or glass might be better.
