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unstable tank and fish deaths

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I've experienced a number of problems with my tank and I thought maybe someone here could help. In the past couple weeks I lost all my badis, a number of shrimp, and just today I lost my beloved halfmoon betta.

My tank is a 12 gl fluval edge and is close to 3 years old. It's planted but not too heavily. I do 30% water changes every week. For the water change I use 2gls of tap water (that rests overnight and add 2 drops of Prime) mixed with 1 gl of RO water with 1 little scoop of GH Up. I also add 6 drops Phyton Git, 32 drops Flourish Potassium, and 2 pushes of Green Brighty Step 3 to the mix. If I trim plants I add 7 drops of Green Gain. I dose potassium every other day and two pushes of Green Brighty Step 3 every 3 days. Due to the tank's age, I have added Iron Bottom to the substrate.

This routine has worked for me but recently I started to notice that plants appear stimulated by the water change and photosynthesize for 24 hours but then stop and I do not see anymore oxygen bubbles being released for an entire week.

co2 is administered via an inline co2 diffuser at 1 bbl per second. For light I use the Fluval Edge's system that came with the tank plus a Padlite with two LED strips (one white/one roseate). The co2 drop checker always turns yellow just after a few days, indicating a dangerous accumulation of co2.

The temperature is kept steady at 76F. In the past year, I'd been getting cyano blooms and I have added a product called Blue Green Slime Stain Remover by UltraLife every now and then and it seems to do a good job as cyano disappears for 3-4 months but then comes back again.

Just after my betta died I did a number of tests:

PH: 6.2
KH: 30mg/l
GH: 100
Nitrates: 10mg/l
Nitrtites: 0
Ammonia: 0

any ideas what's going on? any tips to stabilize my tank, bring PH to 7.0? why do plants stop photosynthesizing?

Thanks!
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The plants aren't releasing oxygen as you think after a water change. That is probably nitrogen or another gas in the water that is being released as it warms and as the partial pressure changes. That happens to every tank, regardless of plants.

In terms of your losses, firstly I would double check your nitrate and other levels. The nitrate (in particular) are notorious for being inaccurate. Shake the two bottles (assuming your're using API) for a good 60 seconds. Then test again. Also can you test phosphate? I haven't done the calcs but it looks like you may be adding too much ferts for that tank.

Also, stop using that cyano remover. It is either a nasty chem or an antibiotic. This will destroy your biological filter.

Turn CO2 off for now.
Do a large water change. Just add prime and tap water, nothing else.
Let it come to temperature and then slowly modify kH if you so desire.
Get it to 3dKH as a minimum. Measure the pH and record both these figures.
Leave it at temperature and kH for 24 hours.

The next day measure all settings again and then add then adjust the mircos as required. Leave it a day and adjust macros if needed.

Basically start again, reset and watch the ammonia etc.
 

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Since I don't have any Prime I can't just read the label, but that two drops sounds off to me. You would need to check the tap water before you put it into the tank to find out what the PH is, but likely the RO is responsible for the 6.2 PH.
CO2 should come on about one hr before the lights come on and shut off like half an hr before they go off each day.
 

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Yes, according to the dosing requirements, (5ml / 190L) = 7 drops of prime for every 3.6G (30% of 12G) during your water change.
 

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Discussion Starter · #7 · (Edited)
Yes, I can definitely see the oxygen bubbles coming off the plant leaves within an hour or two after the water change. My nitrates were 10mg/l. I'll get a phosphate test kit. How do you suggest I modify KH?

No, the fish deaths have not happened after using the cyano remover. Last time I used it was 4 months ago. The fish deaths have happened when the drop checker turned yellow indicating a co2 overdose.

The reason i put only two drops is because the tap water rests overnight and also the scoop of GH UP I understand primes as well. The whole purpose of adding GH UP is to buffer the RO. I doubt that 1gl RO buffered with GH UP out of 3gl water change would cause such a spike in co2.

For now I turned the co2 off and added an oxygen pump. I will measure KH tomorrow and share the results.
 

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I don't know if it effects the CO2 or not but the concern here is that lower than 3KH results in unstable PH. KH helps regulate PH.
Chlorine dissipates quickly but most cities use Chloremine which doesn't.
But two drops in each gallon seems to be the correct amount if it's put
into each gallon when you set the water in the bottles to sit overnight.
 

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Discussion Starter · #9 ·
That's a great point. So 3KH is about 30mg/l?
Would the low KH/PH swing affect photosynthesis?

This is the link explaining GH UP:
http://www.theshrimptank.com/water-conditioners/borneowild-gh-up-90g/

Do you think a 3gl tap water 1gl RO/GH UP ratio instead could make a difference?

I almost seem to think that the new GLA co2 bubble counter I added is letting co2 randomly into the tank. Once I caught it overdosing co2 and tightened the co2 release down. That was last week when all the badis perished...
 

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3dKH is 54mg/L
 

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I think the PH swing being bad for the plants is possible, but mostly on those that list
a noticeably low PH. Some sites(very few) which sell plants list the PH they "need".
I have no study/training in that to say for sure, but I believe it to be the most common place to find them growing and that you will find them in other PH levels as well.
There probably are a few exceptions to that.
Once I saw that the link was for Borneo I didn't read any farther. They don't sell junk.
Lots of the people who use that have very expensive shrimp and wouldn't use stuff
that might harm them.
Is that bubble counter integrated into the regulator on that CO2 rig ? The regulator would be the part that I would suspect would allow or not allow the amount that goes out.
 

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Discussion Starter · #12 ·
No the bubble counter is separate from the regulator. What I am trying is to limit the co2 further, from 8-9 hrs a day to only 5-6 hrs a day. This morning my PH was 7 and my KH 20mg/l
 

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To raise the KH add baking soda at the rate of 1 teaspoon per 30 gallons. This will raise the KH by 2 German degrees of hardness, which is equal to about 35 mg/l.
For a 12 gallon tank I would try 1/4 tsp. and allow that much to dissolve and circulate, then test the KH.

Potassium bicarbonate will also raise the KH. It is dosed a bit less than baking soda. It would be OK to try 1/4 tsp and check the KH.

Either of these materials dissolve very quickly. You could shake some in a jar of water and spread it over the water surface, it will mix quickly, and you can test as soon as it has circulated.

When altering the TDS (Total Dissolved Solids- which includes the salts and minerals we are talking about, make small changes, let the fish adjust for a week, then another small change. Also, some of these materials are used by the plants as fertilizer, some plants can use the carbonates as a carbon source.
So dose, then run it for a while, see the overall result before you adjust the dose.
 
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