Bubble Wands, Filters

Welcome, Mizuti. 

Glad you are enjoying the early stages of your hobby - it is indeed exciting and addictive.

Others with more experience on the specific aspects you mention (bubble wands and all-in-one 125-litre tanks) might be better placed to answer those questions, but, in the interim, what brand of tank were you thinking of getting? It might be that some brands come with better filters and heaters. As far as filters are concerned, Fluval and Eheim are generally known to be good brands.

Looking at your water company website, what are the readings (in degrees French/German/Clark) for water hardness? That should help get you started on what fish would be most suitable for your water.

You might find these helpful:
https://forums.thinkfish.co.uk/fishtank-filtration-and-cycling/fishless-cycling-how-to-do-it/
https://forums.thinkfish.co.uk/fish-tanks-and-equipment/heater/msg34327/#msg34327 - a recent thread on heaters

Hope that helps.

Bubble wands are not necessary, they are used because fishkeepers like the bubbles. A lot of people think bubbles are needed to aerate the tank but they only do that by moving the water round. A filter with the water outflow correctly positioned does that job better. If you like the looks of bubbles, it is fine to have a bubble wand, but if you aren't bothered about having bubbles, don't get one - it just ties up another electric socket!
The reverse siphon is overcome by having a one way valve in the tubing. I have a sponge filter powered by an air pump in my betta's tank, and I have a valve between the pump and the filter. You just have to make sure you fit it the right way round 


Fluval U series filters are among the better ones. Recommended turnover is 5 times the tank volume per hour and the U3 has a turnover of 600 litres/hour making it suitable for tanks up to 150 120 litres. It should be fine in a 125 litre tank for all fish except the very few that must have very fast flowing water. The only thing I would suggest with the U series filters is to not use the poly-carbon pads and replace them with just a layer of filter wool.
Should you decide on the Aquael tank, I can recommend Eheim Biopower filters. I used the largest of the three models in my old 125 litre tank, and now have that plus the smallest one in my 180 litre tank. I also like Eheim Jager heaters, though they are slightly wider than most makes meaning heater guards don't fit. This is only important is you have fish that are likely to burn themselves - like my betta who has burned his tail by sleeping perched on the lower sucker 


Edited because I couldn't divide 600 by 5 

The fish that usually burn themselves are those like plecs which like to attach themselves to the glass. They have been known to attach themselves to heaters.

In my main tank I have stiphodons which attach themselves to things like plecs do, but they have never gone near the heater even though it is at 45 degrees rather than vertical. I don't have a heater guard on this heater as I can't find one that will fit. I've had otocinclus in the past and they never went near the heater either.
The only problem I've ever had is with this particular betta. None of the previous bettas have ever chosen such a silly sleeping place.

Hi there and welcome to the forum. 

I've only been keeping fish for just over 18 months now, and from personal experience I can say that it is very, very addictive.
It's great that you're taking time to plan everything, and there is a lot of knowledge and experience available on this forum to help with every eventuality.
I'm looking forward to hearing about your new tank, and hope you'll keep us posted with lots of pictures. 

Those are the holders I have for my heaters, and the betta sleeps on the suckers in between the heater and the glass. His tail droops down from the sucker, and if he's on the bottom one it gets dangerously close the the element.

Once upon a time, they made non-branded versions that has a tube with slits in that covered the bottom of the heater and slotted into the bit with the suckers. I still have some of those although the suckers have long since perished - but Eheim Jager heaters are just that little bit too wide to fit into them.
These http://www.ebay.co.uk/itm/AQUARIUM-ADJUSTABLE-HEATER-STAT-THERMOSTAT-GUARDS-FISH-TANK-PROTECT-PLUS-SUCKERS-/201499395622?var=&hash=item2eea4cc626:m:muGPFm98VqGcLOu1m2g_wQQ are the nearest things available now, but they are also too narrow.

Doh - sorry - brain not engaged. When you mentioned this recently, I had a dig and found a heater guard suitable for an Eheim Jager - but I have a feeling it was only available in USA. I'll have another dig to see if I can find it...

Wow, a Fluval Roma 125 with stand for £50. What a bargain. 

I have several Fluval Romas and find them quite easy to work with due to the lid being in sections. Very handy for having a light on whilst working in the tank. 

Oops, my mistake - or wishful thinking. 
Glad you managed to get it a little cheaper though.