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blackwater tank cycling?

anewbie

Well-Known Member
Messages
1,339
It sounds like you haven't been able to neutralize all of the carbonates. I'd recommend doing a water change and then measuring your baseline water parameters (EC/TDS and KH). If it's quite high, you may need to dilute it out first. Then, take water samples and do your pH lowering experiments outside the tank. See how that water behaves before scaling up.

For me, I had to drive the pH down to a pretty low number, at which point it took less acid to keep it there. However, you don't really want to do that with fish in the tank.
baseline is pure ro - tds 2-3 kh 0 and gh 0. Maybe is should double check kh but it is suppose to be 0. I only can measure by degree which is kind of course but will double check tomorrow.
 

Ben Rhau

Apisto Club
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564
Location
San Francisco
That is the baseline for your RO output, but if your remove the sample from your tank after a water change, will you get the same number? Also you don't know your TDS yet.
 

anewbie

Well-Known Member
Messages
1,339
it'll be a few days before i can re-test kh - can't find the kit (just moved) so will order a new one.
 

anewbie

Well-Known Member
Messages
1,339
That is the baseline for your RO output, but if your remove the sample from your tank after a water change, will you get the same number? Also you don't know your TDS yet.
no - the leaves and wood and fishes/food have clearly caused tds to rise - the substrate is pool filter sand (hth) and maybe it isn't totally inert. The tds pen that i used sez the ro water has tds of 2 but the tank is now reading 33. My better ec pen is arriving sometime tomorrow so i'll get a more accurate reading. However - i want to double check the kh now so i'll have to order a new kit.
 

Ben Rhau

Apisto Club
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564
Location
San Francisco
When you use your Hanna meter:
  • To measure pH, I recommend first adding salt (NaCl) to your sample until the TDS > 100. I usually keep a small container of kosher salt with my equipment and add a few flakes to about a 30 ml sample. The sample container needs to be plastic, since glass can cause EMC interference when measuring conductivity.
  • The meter only has a hardwired conversion of 0.5 to calculate TDS from EC. So, if you prefer to use 0.64 (as Darrel and i do) just take the EC measurement and do the calculation manually (or just set a target EC instead of a target TDS).
  • Make sure to order pH standards, so that you can do a 2-point calibration at pH 4 and pH 7. And also a calibration standard for EC (1413 uS). And storage solution for the pH probe. So many solutions!
Hope I'm not saying things that are too obvious. I felt like none of this was obvious to me when I started.

-B
 

anewbie

Well-Known Member
Messages
1,339
When you use your Hanna meter:
  • To measure pH, I recommend first adding salt (NaCl) to your sample until the TDS > 100. I usually keep a small container of kosher salt with my equipment and add a few flakes to about a 30 ml sample. The sample container needs to be plastic, since glass can cause EMC interference when measuring conductivity.
  • The meter only has a hardwired conversion of 0.5 to calculate TDS from EC. So, if you prefer to use 0.64 (as Darrel and i do) just take the EC measurement and do the calculation manually (or just set a target EC instead of a target TDS).
  • Make sure to order pH standards, so that you can do a 2-point calibration at pH 4 and pH 7. And also a calibration standard for EC (1413 uS). And storage solution for the pH probe. So many solutions!
Hope I'm not saying things that are too obvious. I felt like none of this was obvious to me when I started.

-B
I'm not using the hanna meter right now for ph; i'm using ghl continous monitor - also both the ghl and hanna meters came with solution and i calibrated both for 4.0 and 7.0
 

anewbie

Well-Known Member
Messages
1,339
Some data:
the ec pen reads 68 out of the box - have not check calibration; but my tap was 240 and all my cheap grey tds pens indicate tap is 120 so if we assume 2x or 0.5 conversion factor it might be accurate.
-
api kh test kit it turns yellow on 1 drop sadly i don't have anything of finer resolution but the kh is between 0 and 1.
 

anewbie

Well-Known Member
Messages
1,339
This is for the tank? Did you verify the EC of your RO water?
kh is between 0 and 1 i.e, 1 drop turns yellow. The ec pen sez 8; however if calibration is off it will have a bigger impact on ro water for the low range I would think. 8 seems pretty high for ro water.
 

Ben Rhau

Apisto Club
Messages
564
Location
San Francisco
I think 8 us/cm is OK for RO. Mine is lower, but I use the DI stage after RO. You could test the low end of the range by verifying that the meter reads basically zero for distilled water. The EC in your tank (68 us/cm) seems high given your input water.

The pH in your tank is rising because:
  1. There is a source of KH in your tank, however low it is. And/or,
  2. Dissolved atmospheric CO2 is generating KH (which will always happen).
You could isolate the effect of #2 by doing a experiment:
  • Leave a container of RO water out overnight, then measure the pH.
  • Add a proportional amount of acid to your sample as you did to your tank. (You may need to do a serial dilution to accomplish this.) Measure the pH instantly, and then again the next day.
If you find that RO alone is stabilizing at pH 6.5, then it's simply a matter of determining how much acid (e.g. drops per gallon) will neutralize it and then lower pH enough so that it remains below your desired max until the next water change period (1 week?).

If you find that RO alone is stabilizing significantly below 6.5 (remembering this is a log scale) then there's another source of KH in your tank. No choice but to dilute it.

Remember that you need to add salt to accurately measure pH.

Good luck
 

anewbie

Well-Known Member
Messages
1,339
I think 8 us/cm is OK for RO. Mine is lower, but I use the DI stage after RO. You could test the low end of the range by verifying that the meter reads basically zero for distilled water. The EC in your tank (68 us/cm) seems high given your input water.

The pH in your tank is rising because:
  1. There is a source of KH in your tank, however low it is. And/or,
  2. Dissolved atmospheric CO2 is generating KH (which will always happen).
You could isolate the effect of #2 by doing a experiment:
  • Leave a container of RO water out overnight, then measure the pH.
  • Add a proportional amount of acid to your sample as you did to your tank. (You may need to do a serial dilution to accomplish this.) Measure the pH instantly, and then again the next day.
If you find that RO alone is stabilizing at pH 6.5, then it's simply a matter of determining how much acid (e.g. drops per gallon) will neutralize it and then lower pH enough so that it remains below your desired max until the next water change period (1 week?).

If you find that RO alone is stabilizing significantly below 6.5 (remembering this is a log scale) then there's another source of KH in your tank. No choice but to dilute it.

Remember that you need to add salt to accurately measure pH.

Good luck
The ph dropped to 5.98 yesterday and stayed there all day and all night; the vendor thinks micro-bubbles are getting under the ph pen and impacting ph reading. The water is quite 'thick' with tannis and disolving leaves.
 
Last edited:

anewbie

Well-Known Member
Messages
1,339
There is something going on here - and i think the net is good but would like confirmation - only thing it is kind of hard to explain but i will try:

The tank has a sump and when the water transition from the sump intake to the biological filtering it is exposed to air (sort of like wet/dry but not really explicit); because the water is so thick air is getting trapped in the water and when the water is then pumped back into the tank and flows from back to front the front bubble in the air are extremely visible (meaning a lot of air is being trapped in the water); i can of course adjust the flow as the pumps allow for easy adjustment of flow rate from 0% to 100% (gotta love these cheap jebao dcp pumps - not only are they very quiet and inexpensive they are much more flexible than ac pumps); So i think the air is getting trapped with quite a bit of air/oxygen which i suspect is a good thing. Having said that the EC is clearly (too???) high and a water change might be useful this weekend - however i suspect most of the 'stuff' in the water is decaying leaves which is making a thick soup and this sort of begs the following question - is the EC too high that is - is this soup harmful or bad for the fishes ?
 

Ben Rhau

Apisto Club
Messages
564
Location
San Francisco
Air is not being "trapped" in your water. It's bubbling out. But the water movement is a good thing.

The tannins in the water are good for your fish. When you say it's "thick", do you mean it's viscous? That sounds like some mixture of protein, lignin, bacteria and fungus. All normal. It will resolve itself, and the key thing you want is water movement, which you have.

The EC isn't too high for the fish to survive, but possibly it's too high for you to easily lower the pH. Depends on where it's coming from. I suggested the experiment above to interrogate that. Personally, I would do a water change to lower the EC, because I think that's likely to make it easier to get your parameters to where you want. That said, you have a very large volume of water. You'll need to be patient and wait it out for multiple water changes. It takes a long time to turn a big boat.
 

anewbie

Well-Known Member
Messages
1,339
Air is not being "trapped" in your water. It's bubbling out. But the water movement is a good thing.

The tannins in the water are good for your fish. When you say it's "thick", do you mean it's viscous? That sounds like some mixture of protein, lignin, bacteria and fungus. All normal. It will resolve itself, and the key thing you want is water movement, which you have.

The EC isn't too high for the fish to survive, but possibly it's too high for you to easily lower the pH. Depends on where it's coming from. I suggested the experiment above to interrogate that. Personally, I would do a water change to lower the EC, because I think that's likely to make it easier to get your parameters to where you want. That said, you have a very large volume of water. You'll need to be patient and wait it out for multiple water changes. It takes a long time to turn a big boat.
But the ph is now showing 5.9-6.1 so do i need to lower ph ? I'll probably do a water change this weekend of 30% if time permits; just to thin out the water. What i meant by the water retaining air - is that i actually see air bubbles in the return water for quite a while as it slowly escape - the tank next to it for example which has the same sump you don't see any air in the water - all the visible air is escaping before it returns to the tank with this tank the air does eventaully escape as you said but it takes consderiably longer. I did dump a huge number of indian leaves into the tank about 4 weeks ago - the bag claimed 100 but i would say it was closer to 15 or 20 full size leaves - i had purchase this a whle ago and was using a leaf now and then on my 10 via the boil tea method; and i just dumped the rest of the package into this aquarium when i set it up (and when i say rest i mean the package still about 90% full).
 

Ben Rhau

Apisto Club
Messages
564
Location
San Francisco
I don't know how to answer on pH. SF recommends keeping wc bitaeniata "at the lower end of the range," which I interpret to be below 5.5. But I'm not an expert here. I suspect pH 6 is not a big difference, and that it's fine to decrease pH slowly over time.

Your water sounds viscous due to organic materials released from your botanicals. I think the main concern is that breaking this down increases oxygen demand. So I wouldn't add more fish for at least a week or two. Water change is probably not a bad idea.
 

anewbie

Well-Known Member
Messages
1,339
I did a water change today and will report results tomorrow. I also calibrated the ph hanna ec probe. WIth calibration it said the ro water was 6 ec and the tank was 70; the aspera ph pen said the ro water ph was around 5.9.
 

Mike Wise

Moderator
Staff member
5 Year Member
Messages
11,173
Location
Denver, Colorado, U.S.A.
I think everyone is over-thinking pH here, if planning to breed most populations of A. bitaeniata. Most actually occur in mixed clear/blackwater streams with softer water values. A pH value of 5.5 was not needed by me for any of the forms that I've kept over the decades. Usually around pH 6 was fine as long as the water had a low dKH <2 and e.c. <70 µS/cm. Instead of 'playing chemistry set' with your tank, put your fish in it and enjoy it!:)
 

MacZ

Well-Known Member
Messages
2,902
Location
Germany
I think everyone is over-thinking pH here, if planning to breed most populations of A. bitaeniata. Most actually occur in mixed clear/blackwater streams with softer water values. A pH value of 5.5 was not needed by me for any of the forms that I've kept over the decades. Usually around pH 6 was fine as long as the water had a low dKH <2 and e.c. <70 µS/cm. Instead of 'playing chemistry set' with your tank, put your fish in it and enjoy it!:)
Basically my approach. Keep TDS down and you're good.
 

anewbie

Well-Known Member
Messages
1,339
ok. Hopefully the water change will lower the ec - will report tomorrow. Kind of wish i knew for sure what was causing the high ec - if it is simply hte large number of leaves/wood or some other goof. I used the same substrate in another aquarium (hth pool filter sand) and have not seen any adverse numbers on the ec relative to tap.
 

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