i'm not sure but has anyone tried a similar shape tank, with an external sump tank with high surface area that is part of the filter cycle and would help with the oxygen of the main tank? (would be tricky to hide though)
That would work, yes.
Thanks for the welcome fish....ok guys, here are a few pics, not great but I think they will suffice. The ornament covers the suction pipe which leads down to a major fluval filter (about the size of a car battery) housed in the base, from which an outlet pipe is connected to the base of the long white tube which channels the water back into the tank.
There is a pond 2 pump, also housed in the base, which feeds the air stone, so plenty of surface activity.
It looks interesting, can you show photos of the filter?
I am slightly concerned that you do not have enough circulation..
In the local fish shop there was a column tank half the height of this one that was very well stocked indeed, definately a shoal of tetras and lots of rainbow......somethings, quite a few bottom feeders and also some larger fish too, it looked really well populated. Which leaves me a little confused about the low fish quota mentioned due to low surface area.
The shop does not care if a few of their fish die every so often or if the fish have a good life.. what they care most about is selling you that fish tank (which they already succeeded at) and fish (also success there). Now when (if you do not read up about fish-in cycling), the fish start dying and you go back, they'll say "it's normal, just get some more to replace them" and they would have effectively gotten more cash out of you.
So, I really strongly recommend (for the sake of the fish and for the sake of your long term success at fishkeeping):
1. read about fish-in cycling of the filter (beginner's resource has a LOT of information on here)
2. buy a liquid test kit for ammonia, nitrite, nitrate, pH, hardness (API Master Test Kit is a good one)
3. every time ammonia or nitrite starts to reach 0.2, do a 50% water change (part of fish-in cycling) because readings of over 0.25 will harm the fish in the long term
About the plants, I forgot to mention.. I would recommend Elodea as it can easily grow that tall, but you will have trouble getting it down.. how about, get a normal, black, plastic plant pot, pot the Elodea into there, wrap a layer of fine filter wool around the pot (preferably black of dark green, using nylon string), then attach some Java moss to the filter wool (also using nylon string). To lower, there are implements available which will let you reach into the bottom of the tank..they are a bit like the ones used when people go around picking up trash off the streets.. they might even be the same ones! At any rate, those things are sturdy enough to allow one to take big rocks out of tanks.
p.s. The fish the shop sold you are not Pentazona barb (Puntius pentazona), they are actually green tiger barbs (Puntius tetrazona). Goes to show about how much they care..
p.p.s. Puntius tetrazona are nippy #19###s, they will limit the other fish you can keep by quite a lot.