if u can afford the chiller then go for it..
if u go for the aircond also better..lucky my tank in my room and my room got aircond..so my temp can go down to 22C   
well 22C can only be achieved at night..when i sleep..
so to benefit from the cold..i on the lights atnight..and off em in da day!
summore in d day off lights..off aircond also..temp wont go up cuz lights arent on!

moss can grow kao kao

wah got fengshui wan ah..how u check? my fengshui ok ah?

icic.........
i must have already forgot that u mentioned that........

y not change to bigger tank??

MTS - malaysian trumpet snail. they are quite beneficial to the substrate since they dig and mix the substrate (like caing). dont eat plants too. only bad news is they're quite an eyesore hehe
even if your mosses are 'old' they should be growing at least. try to figure out the cause first.

DIY CO2 is almost like that lah 1 week

coldfusion,
need to get your lighting up fast. Before your plants yellow. Also, do consider adding driftwood tied with a bit of java moss to make things look more interesting.

For layout, I guess if you landscape your slope from back to front, your tank will look much bigger. Also, please consider some midground plants.

For DIY yeast, i go with 1/4 yeast, 1/2 baking soda, and 2 cups of sugar for a 1.5 litre bottle.

For the Nutrafin CO2 bottle, I use slightly less than 1/4 yeast, 1/2 baking soda, fill sugar up to the first indicator and water up to the next indicator.

More yeast = more CO2 generated but runs out much faster.