Okay well i have a number of questions on what i should put into my 30g fish tank that i will be putting my flowerhorn in. Should i put a little bag of crushed coral in the tank to help out the PH? and my brother has a reverse osmosis 3 way filter and i was wondering could i use that water to do water changes into my tank?

Thanks

RO water is not a good idea for flowerhorn because it very low in PH and water hardness.