Sorry Paul this ain't gonna be pretty so don't take it the wrong way:
My tank is 6x2x2 as the title says.
Big tank. Wants big filtration which is pricey. I wouldn't gamble on buying budget filtration here.
CO2 will be 2 x homemade pop bottles fed directly into filter intake
Waste of time. You will need 20 bottles for the tank and then it will still not perform too well. One thing I may be missing but won't the filter just suck the mixture through into the filter? Either get 1 and probably 2 pressurised or forget CO2 altogether
Lighting will be 2 x 400w-GROW-LIGHT-KIT-BALLAST-SHADE-AND-BULB
You're kidding right? 800W over a 180 gallon tank? Why grow lights? Just get 3 x full length T8s or T5 standard tubes (forget T5HO) with reflectors and ballasts etc. You are not going to need any more than that and it will save you a fortune on electricity.
Fiddling with the height to get it right? Unless you live in a converted warehouse with high ceilings then please forget this one.
The external filters are good, they are pretty much a copy of the tetratec ones
Is this a good or bad thing!!! If its a copy of a Tetratec then I would assume its even worse!!! As said before DO NOT skimp on big tanks filtration. The budget ones still cost a fair bit and that means more money to waste. FX5 or Eheim IMO on your tank.
Compost from B&Q, or dig soil out from the garden, spread it thin on some polythene and leave in the sun for a week or 2. Then cap with gravel.
Personally I'd be either visiting a beach at midnight with a fair few buckets or geting some playsand. Maybe (and I haven't read this anywhere so I will let you research if it has been done) you could get some black food colouring and stain the sand. Then leave it all to rinse for a fair while?
The hobby in terms of understanding has moved on in giant steps over the past 5 years or so, to the point where the people who rave on about high light needs have very quickly been caught up by the people who actually understand plants a little better. Look at it as those who just followed compared to nowadays where there are many that want to learn and question.
Light and the term 'highlight'is something that is about to be shattered in a big way and a lot of those who defend their beloved 'lighthouse' setups are going to be a little tetchy once it happens. Saying that I have been using the term 'about' for a while and we haven't reached that yet.
Needless to say if you go onto the forum(s) where people learn and question rather than the ones that just distribute the old myths of the hobby then you will see that far from people having highlight and thinking they need it they are actually cursing the day they bought it and end up raising them 2ft above the tank trying to reduce it and gain spread.
These days it is not about the quantity. It is about how well spread it is, coverage etc. Now this change in thinking has been building for a while buit the advent of LED just confirmed it to many and cleared up some of the quandries.
So as I have been saying for absolutely ages already WATCH THIS SPACE
So 800W Nope, Grow lights, I'm chuckling. 3 standard W flouro tubes the full length of the tank is more than enough.
AC