The question in my mind is the balance between smaller - so a smaller mouth and can eat only the small fry; or bigger and so cannot go where the fry may hide.

Then add a fish. I don't need many...probably only 1 or 2. The tank is small and I don't want to overload it anyway. I just want something swimming to look at other than shrimp. Less fish also means (hopefully) less fry get eaten too. DarkOne isn't wrong about the price being high. I bought that Fluval because I knew it would fit, but I also just bought the Aqueon Pro for another betta tank I have set up at my office, and it would definitely fit as well. Also, five years later my Fluval heater still works, and the glass sleeved 50W Tetra heater I got with my new betta tank (from my sister) did just as I have noted...failed "on" and took the tank to about 86 degrees. Finally, if you are not going to spend the extra money on an external controller or a model with electronic controls, consider selecting a heater that is slightly undersized. This will at least lessen the carnage if it fails ‘on’ and will give you more time to notice the problem and react before things get out of hand.

Fluval Spec V Black 19L Glass Desktop Aquarium

There are two ways to combat this problem. The first is to invest in an aquarium heater that has advanced electronics for the temperature control. The problem is that most heaters in this category do not fit in the pump section of the Spec. The Eheim Jager is a great example of one that does offer better reliability and control, but unfortunately does not quite fit in the Spec V.

I always think bog wood looks a little boring in a larger tank, but in a small Flex tank with some pants around it can be quite a feature. After messing around with the pump in several rotations, I don’t think it matters much if the pump is oriented with the inlet pointed toward a wall instead of the filter section.The Fluval Spec 19 Litre Aquarium in white also comes with Carbon media and Biomax rings (3 stage filtration)