# DIY CO2 dropping pH to >=6.0, worried about my Cory cats.



## cathyinz (Feb 19, 2018)

EDIT: It's occurred to me that this might be better in the freshwater forum instead - sorry! I will crosspost it when I get home.

Hello! I'm still a beginner with plenty to learn. This post is about my ten gallon tank that I've stocked with the following:

Fish:
8 x corydoras habrosus

Plants:
Ludwugia repens
Some variety of sword, reddish and bought from PetSmart
Dwarf chain sword
Cryptocorne parvae

Misc.
Pool filter sand, NatGeo fine black gravel as substrate
Aqueon Quietflow 10 filter
Eheim Jager 50W heater
2 x 28W CFLs (Phillips bulbs)
DIY CO2 system using 1c sugar, 1/3 tsp yeast and a pinch of baking soda
An ugly oversized terracotta pot
Some rocks

Water conditions: I cycled for a month using Dr. Tim's ammonia, and I saw spikes in nitrites and nitrates. Where I messed up was assuming the cycle was complete when all the nitrites were gone. As it turns out, I believe my cycle stalled due to the acidity of the water, which started out at around 7pH but dropped to maybe 6.2 near the end due to nitrification. I figured a water change would fix the ammonia levels quick enough to add fish, but nope.







Water conditions are 0.5ppm / 0ppm / ~20ppm. Water temp is 75F.

I wanted to get into a high tech set up, but I realized the CO2 was dropping my pH levels to near 6.0, possibly lower. Tap water that I've left sitting out for 24h registers at 6.8-7.0. I've read that KH plays a large part in how easily my pH swings, and that I can use baking soda or crushed coral to raise KH. I don't have a GH/KH test kit yet but I'm looking to purchase one today.

My cories, for the most part, are a little lazy? Half of them seem content to just sitting on the sand in small groups. The other half are snuffling around, swimming around, and exploring the tank. Their gills are just a tad red, I'm guessing from ammonia and the acidic water.

My plans to improve my cories condition:
- monitoring ammonia levels daily, doing 20% water changes if the ammonia goes to 1ppm or if their behavior is off.
- dosing with Prime so the little guys are ok.
- leaving the CO2 system disconnected for now, so that the pH can restore itself to at least 6.6.

Questions:
- Would crushed coral or baking soda impact my cories negatively?

Suggestions on what to do (large, more frequent water change? Add baking soda?) are very much appreciated!

Bonus: Cory sitting on a leaf


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## Gardener (Feb 13, 2011)

Yes, you are going to have to add some baking soda. Essentially when adding CO2 you are trying to get 20 to 30 ppm CO2 for optimum plant growth. Some even go higher (myself included). There are two ways to measure CO2 concentration. It can be calculated, based on pH and KH concentrations (https://barrreport.com/threads/co2-ph-kh-table.10717/), but as you said you don't have a KH test kit. The other method is to compare pH of completely off-gassed tank water with the current pH of your tank. CO2 concentrations of regular water is about 3 ppm, so since pH is a logarithmic scale a pH difference of 1 gives 10 times more CO2, or in other words 30 ppm - your target concentration. As you have noticed, that will drive the pH too low without the addition of any baking soda to give you a higher starting pH. In a 10 gallon tank I would suggest adding about 1/8 teaspoon of baking soda and work your way up slowly from there over the course of a few days. Don't forget to add a bit more whenever you change your water, the amount depending on how much water you are replacing. Oh and my band of emerald corries are quite happy with baking soda being added to their tank 

Another thing about adding CO2 is that plants like consistent concentrations. And your fish will appreciate a reasonably constant pH. Both can be hard to accomplish with diy CO2, but many have had success. Just be careful once the yeast mixture starts running out, as your pH will then slowly start to climb again.

One last thing, Prime will lock up the ammonia/nitrite in your water and can be used in an emergency. However be aware that after 48 hours it starts to release it again.

Good luck with your tank!


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## EDGE (Aug 24, 2010)

Greater Vancouver water comes out at 20 to 40 uS. Tap water has very little to 0 gH in there. You need to add gH to the water. I can see calcium deficiency in the new growth of the ludwigia on the right corner. 

The ppm 0.5 / 0 / 20 ppm is ammonia / nitrite / nitrate? If this is correct, the nitrite got converted to nitrate which is why it is 0. 

Add Phosphate, potassium and trace to help the plant start growing. 

With Seachem equilibrium, adding phosphate should be good for now until your nitrate start bottoming out. Get the gH to around 3 with Seachem equilibrium. 

Use Seachem Phosphorous and Seachem Flourish 

You can mixed your own with dry fertilizer (mono potassium phosphate) and CSM +B (Plant prod micro nutrient)

Personally, I would keep things simple as a first set up and use Seachem flourish and Seachem phosphorous. Easier to get things from 1 store than run around getting dry fertilizer, scale, bottle, measuring cup / dropper etc.



Your pH will climb a bit when plants are using the nitrate.


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