bigfishhead

No worries. Some products enhance your fish color very well and sometimes the color looks almost unreal. But everything comes with cost once you stop using them your fish loss color in a week. 
New life spectrum cichlid formula is the way to go. NLS does not like some other product that contains color enhancement ingredients that gona shorten your fish life into half. I feed my cichlids only on NLS 1mm formula. It make my cichlid health and happy. And of course showing REALLY nice color. 

+1 to what camtang said above.
You like brightly coloured cichlids and your tank size is limited for 240L. And base on what stock we have in NZ, haps and tangs are generally too large for your tank size. Dwarf Tangs or shelly dwarf dont have that brightly colour compares to mbuna and peacock. Tropheus setup is nice but in NZ it is pretty hard to get decent stock supply and these fish needs extra care than mbuna and peacocks.
I would say mixed mbuna or all male peacocks would suit you the best right now.
As for the substrate, try to use bright white fine substrate if possible. Cichlids likes digging. I would suggest fine white coral sand. It lights up cichlids' colour the best.

After playing around with a few different combos, it is defiantly possible to mix them, but in my opinion I think it is best not to do so. 
Tangs are not from Lake Malawi, they are from Lake Tanganyika. 
Depending on your foot print on your 240, you could do a male peacock show tank, a dwarf tang tank, or maybe a small mixed mbuna tank- yellows, rusty, snow white etc. But in all honesty, your 240 is on the smaller size for Africans- not impossible, but does throw up a bit more issues.

Yellow and Demasoni are the classic combination for Malawi cichlids tank setup. They are my personal favorite still.
You can get away with small tank size when they are young or juvenile size. But eventually you will need a 180L or plus for group of Yellow and demasoni.
For tank size, a classic 1.2M tank with dimension 1200mm L X 400mm W X 400mm H (190L) is a good start, or 1200mm L X 500mm W x 400mm H (240L) is even batter. Malawis especially Mbuna are more bottom layer fish. You need tank footprint much more than height.
For fish number, it depends on your tank size. Typically you'd better to have dozens of yellows and demasonis in each group. The more you have the less aggression in the tank. For yellows, I would say any number above 6 would be good start. They are not that aggressive most of the time but only during breeding season. For demasoni... thats another story... You can have a singel fish or have a lot, say 12 - 15 to start with or even more if you can. I would strongly against any number below 10.
For red color fish that will get along with Yellow and Demasoni, red/peach zebra. They are same as yellow not so aggressive as demasoni... So just get serveral to keep themselves as a company. The other option would be dragon blood but they might grow pretty big later on. But if you raise them and grow them out with yellows and dems from young they wont grow that big due to in the same small tank, get a couple if you like them.
Good luck on your setup.

Yellow and Demasoni are the classic combination for Malawi cichlids tank setup. They are my personal favorite still.
You can get away with small tank size when they are young or juvenile size. But eventually you will need a 180L or plus for group of Yellow and demasoni.
For tank size, a classic 1.2M tank with dimension 1200mm L X 400mm W X 400mm H (190L) is a good start, or 1200mm L X 500mm W x 400mm H (240L) is even batter. Malawis especially Mbuna are more bottom layer fish. You need tank footprint much more than height.
For fish number, it depends on your tank size. Typically you'd better to have dozens of yellows and demasonis in each group. The more you have the less aggression in the tank. For yellows, I would say any number above 6 would be good start. They are not that aggressive most of the time but only during breeding season. For demasoni... thats another story... You can have a singel fish or have a lot, say 12 - 15 to start with or even more if you can. I would strongly against any number below 10.
For red color fish that will get along with Yellow and Demasoni, red/peach zebra. They are same as yellow not so aggressive as demasoni... So just get serveral to keep themselves as a company. The other option would be dragon blood but they might grow pretty big later on. But if you raise them and grow them out with yellows and dems from young they wont grow that big due to in the same small tank, get a couple if you like them.
Good luck on your setup.

Yellow and Demasoni are the classic combination for Malawi cichlids tank setup. They are my personal favorite still.
You can get away with small tank size when they are young or juvenile size. But eventually you will need a 180L or plus for group of Yellow and demasoni.
For tank size, a classic 1.2M tank with dimension 1200mm L X 400mm W X 400mm H (190L) is a good start, or 1200mm L X 500mm W x 400mm H (240L) is even batter. Malawis especially Mbuna are more bottom layer fish. You need tank footprint much more than height.
For fish number, it depends on your tank size. Typically you'd better to have dozens of yellows and demasonis in each group. The more you have the less aggression in the tank. For yellows, I would say any number above 6 would be good start. They are not that aggressive most of the time but only during breeding season. For demasoni... thats another story... You can have a singel fish or have a lot, say 12 - 15 to start with or even more if you can. I would strongly against any number below 10.
For red color fish that will get along with Yellow and Demasoni, red/peach zebra. They are same as yellow not so aggressive as demasoni... So just get serveral to keep themselves as a company. The other option would be dragon blood but they might grow pretty big later on. But if you raise them and grow them out with yellows and dems from young they wont grow that big due to in the same small tank, get a couple if you like them.
Good luck on your setup.

Good one. These funny characters deserve a good home. Keep us posted.

So true, had a 6 foot with xxl clowns for 10 years then due moving had to sell so very excited to now be able to offer forever homes to these beautiful , funny fish

Nice. Good to see another clown lover.
I've been keeping good size clowns for years. Decent size ones are pretty hard to find. (15cm+) 
But It is definitely pleasure to watch them schooling once you have a decent size group of them. 
Good luck on your project.

Some photos taken today of a few of the corals. Progress is slow at the moment, haven't really had much spare time to spend on the tanks.

No worries. For your two tanks, tank one is better than tank two.