barrage of questions regarding co2/kh, water changes
a few months back I tried to change my 29 from a walstad type low light tank with a crappy stock light w/ huge amazons and crypts to a higher light mostly stem tank. I bought a 30 inch aquasun fixture with 2 24 watt bulbs thinking hey thats not too much light, thats only 1.6 wpg but no, its a crazy amount of light(especially considering the lack of co2).
I have a ton of plants in the tank but they don't seem to be growing as fast as lower light tanks ive had in the past, I'm sure they dont have either enough nitrates(almost always at 0ppm) or co2(i dont supp). I would like to start with a diy setup until I understand the water chemistry and everything better and then move to pressurized. I have some questions about ph/kh though.
my kh is almost always less than 1, my test kit is supposed to turn from blue to yellow but it turns yellow with one drop so I have like no carbonates. my gh was at 5-6 which seems fine. I've heard multiple different things about kh and co2, some people say you need at least 4dh whereas some say you dont need any. it seems like my ph which is hovering around 6.6-6.8 would go down to like 5 with the addition of co2 and i cant see my fish appreciating that.
I threw a handful of crushed coral in my tank to see if that would raise the kh so i could setup my co2 but the kh is still <1 and the gh has risen to like 11 or 12. I'm assuming that my plants are taking up all the carbonates, should I just use baking soda? I'm hesitant to use it because I think sodiums bad for plants.
I'm also wondering why/when water changes are necessary if your nitrates or phosphates aren't high, my nitrates are always at or around 0 and my phosphates at like .25.
last question is if dosing dry ferts is necessary for high tech tanks, i would really like to get away with just using flourish a few times a week which is what I'm currently doing but with meh plant growth.