Hi, welcome to the forum
Do you mean the Juwel Primo 70? That has a footprint of 61 x 31cm. The filter that comes with the tank has sponge media so that's fine - just don't replace them like they say (every 3 months).They will last for years and only need replacing when they fall apart or won't go back to shape after washing them. All you need to do is squeeze them gently in water that you take out during a water change.
Juwel are one of the better manufacturers.
Could you fit a longer tank in the space intended for a tank? If you could, that would give you more options for fish as a lot like more swimming length than 60 cm. For example the Juwel Primo 110 is 81 cm long, and the Rio 125 is also that length just taller.
Eheim is also another good make with two ranges of tank at 80 cm long. Be warned though - I had their Aquastar 54 which claimed to be a 54 litre tank. That was just the space occupied by the tank and didn't take the thickness of the glass or the air space above the water into account so Eheim's tanks hold less water than they say even when there is nothing in the tank. Juwel's tanks do hold the amount of water they say though by the time you've put sand or gravel and decor in, they do displace some water.
You can also pick up second hand bargains - see if there are any on Ebay in your area. The things to look out for a cracks in the sealant and scratches. Ask to see a second hand tank filled with water to check for leaks.
With a tank 60 cm long you can't have very big bigger fish. And you need fish that like hard water. I have soft water so I can only suggest the hard water fish I know about. Lilttefish has a
lot of tanks and hard water so she should be able to suggest more hard water fish than me.
The obvious fish for hard water are livebearers; endlers, guppies and maybe platies are small enough for a 60 cm long tank. Swordtails and mollies need bigger tanks. They come in lots of different colours, but the downside is they breed like rabbits and females can store sperm so even having a tank of females means babies for at least 6 months.
@Littlefish should be able to suggest more species.