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
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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
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Edited because I couldn't divide 600 by 5
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