75 gallon Rio Negro blackwater biotope...mostly

[skoram]

from my experience, the farther you get from 7, the less accurate pH test kits become - blue can only become so dark, likewise with yellow. However, test kits are more "reliable" in the sense that they aren't affected by poor or damaged diodes, lack of calibration, etc.

the tank looks stunning by the way, photographs are beautiful too. the difference between this and your first blackwater tank are like night and day. this definitely looks like a true blackwater biotope tank to me - the only thing missing is more leaf litter.

regarding your pH and TDS struggles - the best thing I ever did to address that was to finally invest in an RO/DI filter. I resisted purchasing one for years and tried all sorts of methods, some of which were partially successful, but none remotely compared to the convenience and effectiveness of the RO/DI. I wish I had bought one much sooner. With all that said, I think a pH near 6 and TDS around 80-90 are absolutely fine for the fish you have in the tank. I have a tank with similar species - about 15 Carnegiella strigata, 10 Nannostomus marginatus, 4 Corydoras sterbai and a pair of Apistogramma erythrura. The water conditions are almost identical - pH around 6.3-6.4, 70-80 TDS - and all the fish have been healthy and doing great for over a year. My tank is also somewhat heavily planted with Hydrocotyle leucocephala, Ceratopteris thalictroides, Sagittaria subulata and some sword plants. The benefit of having a tank without extremely low pH and TDS levels is that you can include many more types of plants.

 

[doinkmobb]

the tank looks stunning by the way, photographs are beautiful too. the difference between this and your first blackwater tank are like night and day. this definitely looks like a true blackwater biotope tank to me - the only thing missing is more leaf litter.

Thanks a lot, I appreciate it. I have added more leaf litter since the last photo, I'll try to take an updated shot soon.

regarding your pH and TDS struggles - the best thing I ever did to address that was to finally invest in an RO/DI filter. I resisted purchasing one for years and tried all sorts of methods, some of which were partially successful, but none remotely compared to the convenience and effectiveness of the RO/DI. I wish I had bought one much sooner. With all that said, I think a pH near 6 and TDS around 80-90 are absolutely fine for the fish you have in the tank. I have a tank with similar species - about 15 Carnegiella strigata, 10 Nannostomus marginatus, 4 Corydoras sterbai and a pair of Apistogramma erythrura. The water conditions are almost identical - pH around 6.3-6.4, 70-80 TDS - and all the fish have been healthy and doing great for over a year. My tank is also somewhat heavily planted with Hydrocotyle leucocephala, Ceratopteris thalictroides, Sagittaria subulata and some sword plants. The benefit of having a tank without extremely low pH and TDS levels is that you can include many more types of plants.

My pH wasn't as much of a problem as I thought. It was dropping steadily all this time, but my pH meter said otherwise. I was able to drop the TDS from about 100 down to 70 without too much trouble - 15 gallon water changes weekly brought it down. Now I'm at the point where I'd have to either do much larger water changes or use distilled or RODI water to make a dent in the TDS. My water comes out of the tap at 20ppm, which is awesome. RODI water would be better still, but I'm OK with where the tank is at now. I think I'll shoot for 70ppm and do a water change when it hits 80ppm.

My fish all seem active and healthy; the Colombians are really bright and breeding often (I'd be OK if they stopped actually). I don't think I could do much more to the water quality to make them happier.

 

[skoram]

My water comes out of the tap at 20ppm, which is awesome. RODI water would be better still, but I'm OK with where the tank is at now. I think I'll shoot for 70ppm and do a water change when it hits 80ppm.

20 ppm out of the tap??? I'm speechless ... Most people have tapwater TDS in the 200-400 ppm range. I always thought the TDS of tapwater in Seoul, Korea was particularly low at about 110 ppm. In this case I think you have absolutely no need for an RO/DI system. I'm quite curious though, as to what is raising your water from 20 ppm to 100. My "softest" tank has water with a TDS of about 40-50. This is after adding about 25% of aforementioned 110 ppm tapwater to RO/DI (0 ppm), small amounts of Hydochloric and Citric acid and some blackwater extract. The tank also has a great deal of decaying leaf litter.

I just looked back at some of your previous posts and something seems to be off. You mentioned earlier that your tap has a GH/KH of about 1.5 but at 20 ppm it should be very close to 0. Likewise, a pH of 7.9 or higher doesn't seem possible with such soft water. I would double check your readings as the various values don't seem to correlate.

My fish all seem active and healthy; the Colombians are really bright and breeding often (I'd be OK if they stopped actually). I don't think I could do much more to the water quality to make them happier.

I think fish activity and breeding in particular are the best indicators that your water quality/parameters are good. If I were you I'd just keep doing what you are doing and perhaps forget about all the pH/TDS nonsense.

 

[doinkmobb]

20 ppm out of the tap??? I'm speechless ... Most people have tapwater TDS in the 200-400 ppm range. I always thought the TDS of tapwater in Seoul, Korea was particularly low at about 110 ppm. In this case I think you have absolutely no need for an RO/DI system. I'm quite curious though, as to what is raising your water from 20 ppm to 100. My "softest" tank has water with a TDS of about 40-50. This is after adding about 25% of aforementioned 110 ppm tapwater to RO/DI (0 ppm), small amounts of Hydochloric and Citric acid and some blackwater extract. The tank also has a great deal of decaying leaf litter.

I just looked back at some of your previous posts and something seems to be off. You mentioned earlier that your tap has a GH/KH of about 1.5 but at 20 ppm it should be very close to 0. Likewise, a pH of 7.9 or higher doesn't seem possible with such soft water. I would double check your readings as the various values don't seem to correlate.

I know, it's awesome. I was very surprised when I tested the TDS. The tapwater in Tampa was around 250 or more. When I first set up this tank, I added about 15 gallons of seasoned water that had some ferts in it. I then added another scoop of ferts to give the plants a boost, well before I added any fish. At that point, the TDS was over 100. 10-15 gallon water changes made a noticeable dent in the TDS, but the lower I get the TDS, the less of an impact a 15 gallon water change makes. 10 gallons used to drop the TDS by 10ppm, now it takes a 15 gallon change to have the same effect.

The pool filter sand could be having an effect on the TDS and I am feeding a TON of food, to sate the tetras so they allow some food to drop to the bottom. It's amazing how much those fish eat. But yeah, I'm probably just chasing a meaningless number at this point; the fish are doing fine and that's really what matters.

Maybe I'll leave some tap water out for a few hours and re-test the hardness and pH.

 

[doinkmobb]

Males are getting old enough to identify:

There's one more that might be a male also. That would put me at a 3:5 M:F ratio, which I think will work.

 

[doinkmobb]

The males are developing nicely. When the lights hits them just right, they look almost electric. I've noticed a little bit of displaying to the females, but nothing major. No sparring yet either.

The tank is still humming along - pH is just under 5.7, I do water changes when the TDS meter shows 70ppm and it usually drops to 60-65ppm. The juvenile tetras are getting big; I'd say in about two months, I'm going to have a tankful of fully grown and extremely ravenous Colombians. I'm really thinking about rehoming 6-8 of them.

 

[doinkmobb]

I had some spawning activity the other night. I saw that a small female had some eggs on a leaf sheltered below another leaf. She was guarding them ferociously (as best she could, she's tiny) and the male was shooing away other fish as well. Her pelvic fins were a bright orange-red, unfortunately I didn't get a picture. I watched her for a few minutes and then noticed she calmed down; it looks like a cory swooped in and devoured her eggs. Oh well. I'm sure they'll spawn again.

 

[Chris Noto]

Great looking tank. You're teasing me tremendously, as I have an empty 75 gallon tank in my basement right now, but I'm trying to keep my labor commitment to aquarium keeping down these days... All the best!

 

[doinkmobb]

I restocked my leaf litter this past weekend, and almost immediately I saw a female checkerboard defending a patch of leaves in the corner. I'm not sure if she laid eggs or was just claiming a territory. I'll try to take an updated picture of the tank soon.

I've been slightly lazier as far as keeping TDS down - I was trying to keep it between 60-70, but now try to keep it between 70-85. My pH meter needs to be calibrated again, so I'm not sure what it is now. Somewhere in the mid-high 5s I suspect though. The lowest I ever recorded it at was 5.66. The fish are happy so I don't think I need to chase specific numbers.

 

[doinkmobb]

 

[Chris Noto]

I absolutely love what you are doing with this tank. Doing something like it, on a similar scale, has been a dream of mine since I was a little boy, back toward the middle of the previous century. The only thing I'd like to do that you haven't would be the addition of a group of Angels, Manacapuru Red Shoulders being my current faves.

Many thanks for the information and motivation that you are sharing!
All the best.

 

[doinkmobb]

I absolutely love what you are doing with this tank. Doing something like it, on a similar scale, has been a dream of mine since I was a little boy, back toward the middle of the previous century. The only thing I'd like to do that you haven't would be the addition of a group of Angels, Manacapuru Red Shoulders being my current faves.

Many thanks for the information and motivation that you are sharing!
All the best.

Thanks. If I had to do it over, I think I would recreate this setup on a smaller scale. When we eventually move and I have to break the tank down, I'll probably give the checkerboards their own 33 gallon long and set up the 75 for a small shoal of Biotodoma cupido. I really like the amber water and messy leaf littered look, but I want to try for a tidier, clearwater setup next time.