PH/KH VS. Drop Checker - The Planted Tank Forum
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post #1 of 4 (permalink) Old 05-31-2014, 10:10 PM Thread Starter
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PH/KH VS. Drop Checker

I am going to wear you guys out with all of my questions, but here is another:

I use a 10 gal. tank to grow out plants for the bigger fish & plant tank.
The plant tank has a Flourite sub-strait, and DIY CO2, no fish. When I do the PH/KH calculation, (a KH of 5 and a PH of 6.2,) I get a CO2 reading of 95, very high. But the drop checker is showing a lime green, indicating that things are OK, just a little on the high side. I certainly would not put fish in that tank because the CO2 is bubbling at around 20 per minute, and I am sure that the water is very acidic with little oxygen. So how accurate can the drop checker be?

I ask because I am thinking about adding CO2 to the larger tank w/fish and plants. However, I certainly don't want to do that until I am sure I can control things and have an accurate way to measure the water parameters. So my question is: Why the extreme difference between the drop checker and the PH/KH calculation? ... Phil
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post #2 of 4 (permalink) Old 05-31-2014, 11:39 PM
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Neither are that accurate that you can rely on them. They are just helpful in a starting point. To many people rely on these to dial in their co2. Then they have algae problems and growth problems and cannot figure out what the problem is. When it is usually not enough co2.

There are things you want when running co2. You want a good way to get the co2 into the tank. You want your co2 to be stable. Same everyday. You want nice surface disturbance to help get some o2 into the mix. You want good flow throughout your tank.

Get these things right and then use your plants growth and the fish to dial in where the optimum co2 level is. There is no substitution for this period. No fancy gizmo .... regulator ..... piece of glass with a solution in it. You have to ignore those things. They may be a starting point but that is it.

Do not be afraid to add a few fish to your co2 tank. Just be there for the day when you do. If they begin to gasp add surface agitation to get the o2 up. If they do not then you want to drive the co2 up until you see them starting to go to the top. Then back it down a little or add a little more surface movement. The fish do not croak immediately as soon as co2 gets a little high. They will let you know when it is high. Then adjust and watch. You need to have a day or two to watch this.

Good luck.
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post #3 of 4 (permalink) Old 06-01-2014, 12:53 AM Thread Starter
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Thank you. That confirms what I thought I was seeing. I guess what we need is a controller that is based on the amount of oxygen in the water and the PH.
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post #4 of 4 (permalink) Old 06-01-2014, 01:54 AM
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First, set up the tank so there is adequate water surface ripple, so the entire water surface has distinct rippling, not splashing, just rippling. Next, if you really want the ability to use high CO2 and high light, use a wet/dry filter, which will ensure that you have high dissolved oxygen content in the water.

The tricky part is finding the nerve to jack up the bubble rate high enough. When you have fish you will probably attribute every twitch a fish makes to CO2 distress, and be reluctant to increase the bubble rate enough. But, if you use a drop checker, with 4 dKH water in it, you can ignore what the fish do until you get the drop checker liquid a nice green color. You will probably still be short on CO2, so you can start a slow adjustment of the bubble rate, a small increase every few days, watching the fish for clustering at the top corners of the tank, laying on the substrate, losing colors, etc. which may indicate they are stressed by the CO2. With well oxygenated water you shouldn't see any distress. Also, watch the plants, looking for better growth each time you increase the bubble rate. That could be more pearling, faster growth, healthier looking growth, etc. Stop the increases in bubble rate when you don't see any benefit to the plants from the last increase. Finally, you will have the optimum bubble rate, but only for the current tank plant load and other tank conditions. When the plant growth increases substantially you will probably want to try to increase the bubble rate again.

While doing all of this, concentrate on keeping a clean, well maintained aquarium, without excessive plant density, no dead plant debris, no build up of lots of mulm, clean filter hoses, clean everything, and with regular big water changes.

You still won't know how much CO2 you have in the water - 30 ppm, 50 ppm, 70 ppm??? But, you shouldn't really care either.

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