barrage of questions regarding co2/kh, water changes - The Planted Tank Forum
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post #1 of 4 (permalink) Old 10-25-2012, 08:43 PM Thread Starter
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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.
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post #2 of 4 (permalink) Old 10-26-2012, 02:52 PM
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When your plants are consuming everything in the water column, your water changes shift from having to take things out (i.e. nitrates), to putting things back in for your plants (ions & such).

I would dose baking soda. Sodium is bad, but only in large quantities (in my limited experience).

Lastly, 29 is a tad big for a DIY setup to be effective. You could try a paintball CO2 setup, but if I were you I would just bite the bullet and buy a full pressurized setup. It's a LOT easier to use than DIY. Adjust the needle valve, watch the bubble counter for flow rate, and the drop checker for in-tank concentrations. Green = perfect, yellow = not enough, blue = too much. Easy breezy.

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post #3 of 4 (permalink) Old 10-27-2012, 02:12 AM
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If you have high light you need a constant level of CO2 in the tank, during the photoperiod, every day. You can't do that well with DIY CO2, so high light tanks have to use pressurized CO2 to avoid serious algae problems. I don't know how good that light fixture is, so I don't know if you have high light or not.

If you are willing to spend about $20 you can find out how good the light fixture is. Just buy a Mastech lux meter from Amazon, and measure the lux output versus distance from the light, directly under it, out in the open air (the meter sensor is not waterproof). Divide the lux readings by 76 to get a good approximation of the PAR the light is producing. Then report the readings here.

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post #4 of 4 (permalink) Old 10-27-2012, 11:34 PM Thread Starter
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Originally Posted by Guyver View Post
When your plants are consuming everything in the water column, your water changes shift from having to take things out (i.e. nitrates), to putting things back in for your plants (ions & such).
Isn't putting things in the point of fertilizing? Or are you referring to micronutrients? I think my waters pretty soft to begin with so I don't think doing a water change would do much as far as helping my plants.

in regards to co2, you're probably right, I've read that somewhere around 30g diy becomes kind of a pointless hassle. I'm going to go ahead and spend the money on a paintball setup, but I'm still not sure where my kh should be at or if if it actually matters at all.

I think I might actually do that, I'm planning on setting up a few other tanks in the future so a lux meter could come in handy

one other question I just remembered, is aeration via airstone really necessary? I've read something about having one on a timer so it comes on during the night but I don't recall seeing one in like any of the tanks I've seen online, should agitation from the filter return be good enough?
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