Blackwater Breeding Tank Questions

[skoram]

I have a few questions with regards to a breeding tank I would let to set up for a pair of A. uapesi:

1. Is there a minimum size for a breeding tank? I know this is generally a bad question to ask (and will provoke some strong negative responses on some sites), but I prefer a smaller tank as I will likely have to use purchased distilled/RO water, because homes in South Korea are tiny, and because the size of the tank is inversely proportional to how upset my wife will be when she sees it. The tank will also only house the fish temporarily.

2. Does the color of the substrate matter? I am leaning towards using the same sand used in their current tank, which is bright colored, but if a dark colored substrate will make the fish feel more comfortable, then that is what I will use.

3. Alternatively, are there any drawbacks to using soil as a substrate for a breeding tank? I ask because there are some soils which are rich in humic and fulvic acids which can help to lower the pH of the water.

4. Lastly, as I understand plants are not a common feature in wild, blackwater habitat of A. uapesi. Therefore, should my breeding tank be devoid of vegetation aside from java moss, or could it be helpful to add other plants as well (those that can survive in low pH, at any rate)?

 

[Mike Wise]

These are my opinions/experiences:

1: I prefer tanks with at least 60x30cm 15/20 gallon High) bottom area. This has at least 2 benfits: 1. a more stable water chemistry, which is rather unstable in soft water anyway; 2. more area for separating territories. That being said, if you are very careful, you might be successful in something a bit smaller.

2. I have always used the same light substrate as in all my other tanks. If it appears too bright, then cover the top with floating plants, lower lumins lighting, or both.

3. I would avoid soil because it adds other minerals to the water. I would use a totally inert substrate, like fine quartz sand, which will not leach out minerals. It would be best to use water that is pre-treated with humic acids from separate blackwater-processing tank/vat. You really don't want to 'play chemistry set' with your breeding tank.

4. I would use few/no plants. If the plants die or drop leaves they only increase the polution in the tank. It would be better to decorate with dense clumps of well-cured wood, inert rocks, plastic or ceramic objects.

 

[skoram]

Hi Mike,

Thanks so much for the informative reply. To clarify on the last point, by "dense clumps" do you mean lots of thin branches packed together similar to what's been done in this tank?

 

[dw1305]

Hi all,

These are my opinions/experiences:....
4. I would use few/no plants. If the plants die or drop leaves they only increase the polution in the tank. It would be better to decorate with dense clumps of well-cured wood, inert rocks, plastic or ceramic objects.

I'd have floating plants, it gets around Mike's worry about dead leaves. Because floaters have access to aerial CO2 (and light which hasn't been filtered through tannin stained water), they should be effective at removing nitrogen etc from the tank water.

cheers Darrel

 

[Mike Wise]

Yes, something similar to the tank photo.

Darrel, maybe I shouldn't have written 'polution'. A better word would have been 'bioload'. The lower the better IMHO.

 

[skoram]

Thank you for your input Darrel.

What I am planning so far then is: 15 gallon tank (I'm not even sure my wife will let this go by ... crossing my fingers), sand substrate, heavy leaf litter, dense branches, some java moss and floating plants - I'm leaning towards Pistia stratiotes. I will probably end up purchasing distilled water and soaking it in a tub with peat to lower the pH. It's about 8 dollars for 20 liters but I don't really have any other viable options at this point. I will be moving to a new house in about 6 months and will probably purchase an RO unit then.

I have 2 new questions - first, since distilled water is just pure water, what else should I add to make it suitable for the apistos? I've read elsewhere that I should add some "aquarium salt." Or are there any commercial additives that you would recommend?

Secondly, it seems that Hockey-stick pencilfish (Nannostomus eques) are not available in Korea at the moment. However, several other species of Nannostomus are currently for sale, such as Nannostomus trifasciatus, digrammus, nitidus and unifasciatus. Would any of these be suitable as dither fish?

 

[dw1305]

Hi all,

I have 2 new questions - first, since distilled water is just pure water, what else should I add to make it suitable for the apistos? I've read elsewhere that I should add some "aquarium salt." Or are there any commercial additives that you would recommend?

I think a lot of people just filter through sphagnum peat, and don't add anything else.

If you wanted to add an amount of hardness (dGH/dKH) you could use a very small amount of potassium bicarbonate (KHCO3), magnesium sulphate (MgSO4.7H2O) & calcium chloride (CaCl). These should all be available to you.

There is a calculator at the excellent <"James' Planted Tank - carbonate hardness"> (at the bottom of the page).

Most commercial salt mixes are extremely expensive ways of buying mainly NaCl, but "Seachem Equilibrium" is OK <http://www.seachem.com/Products/product_pages/Equilibrium.html> other than being an expensive method of buying the chemicals named above.

Secondly, it seems that Hockey-stick pencilfish (Nannostomus eques) are not available in Korea at the moment. However, several other species of Nannostomus are currently for sale, such as Nannostomus trifasciatus, digrammus, nitidus and unifasciatus. Would any of these be suitable as dither fish?

I don't really know, <N. digrammus> and N. nitidus are really small fish, and I've never seen either of them. I'm sure they would be fine. M. nitidus looks particularly attractive <Nannostomus nitidus> (all data via TomC).

<Nannostomus trifasciatus> is bigger, and I'd be worried your tank is too small for them. They are lovely fish. <Nannostomus unifasciatus> I also know nothing about.

cheers Darrel

 

[skoram]

Thanks again Darrel. If I ever find myself in the UK I must repay the kindness somehow - or if you find yourself in South Korea.

I have set up the tank (it's a 10 gallon - the 15 gal was about double the cost of the 10 so my wife wouldn't approve) with an approximately 4:1 mixture of distilled and tap water giving me a TDS of around 20 ppm. I also added a bag of peat granules and Indian Almond leaves to the water and, after 1 day, it has already turned very dark brown. I can't imagine any plants surviving in this water aside from perhaps the aforementioned floaters. Even then, I have my doubts ... I also have a sponge filter in the tank but expect that it will take quite a long time to cycle under these conditions.

I am beginning to worry about how I will transfer the fish to this tank once it has cycled, given the undoubtedly big difference in pH and TDS/conductivity. Of course I will have to slowly acclimate them, but the question is - how slowly?

Also, is there any information about how much salt and other minerals should be added to distilled water to make it suitable for these fish?

 

[Mike Wise]

Blackwater fish don't really need - or want - extra salt or mineral. What is extracted from your peat and almond leaves is enough.

As for acclimating, I suggest putting the fish in a small bucket with original tank water about 2 cm deep. Add an air line just to feel better. The fish don't normally need it, but you will feel better. Slowly drip water into the bucket from the blackwater tank until the water is 5 - 6 cm deep. Do this slowly, over about half an hour. Then net out the fish, put them in the blackwater tank, and throw away the water in the bucket.

 

[skoram]

Mike, thank you for clarifying that point for me. I'm relieved that I won't have to mess around with other additives and complex water chemistry. Just distilled water, peat and leaves - nice and simple

 

[skoram]

So I did my first pH check of the tank water today using a Tetra freshwater pH test (which has a supposed range of 5 to 10 - at least those are the numbers displayed on the card) and the result was very strange ... a pH of around 7. Baffled, I tried with an API pH test (which has a range of 6 to 7.6) and the result was the same - about 7. The water is a mix of tap water with a TDS of about 95 (about 2-3 KH and GH using API kit) mixed with medical grade distilled water (around 1 to 3 or 4). After filling the tank, the TDS meter read 30 ppm. A bag of peat and Indian Almond leaves have also been sitting in the water for about 4 days.

Any ideas on why these tests gave such a high pH reading? I actually ordered a digital pH meter from eBay about a week ago so it should arrive any day now. Could it be that since the actual pH is below the valid range, it's just showing up as 7? I just assumed that the color would be equivalent to the lowest pH possible and was surprised to see that greenish blue tint. I thought about the possibility of the sand causing the pH to rise, but given that is called "Biotope Sand Rio" - that would be quite comical indeed. Plus I think it would raise the TDS significantly more.

Here's a photo of my tank from the side - you can see the dark tea colored water:

and the "Biotope Rio Sand"

 

[Mike Wise]

I have 2 questions:
1. When was the last time you calibrated your TDS meter?
2. How is the water being circulated through the peat?

 

[skoram]

Hi Mike,

It's an HM Digital TDS-3 meter which I calibrated just a few days ago using 342 ppm NaCl solution. Also, it's somewhat well-known that the tap water in Seoul is relatively soft.

The water was not really circulated through the peat, just placed in a mesh bag next to the sponge filter for several days.

I should do a current test of the tap water only.

 

[skoram]

I did a quick test of the tap water pH before heading to work. The result was strong blue, definitely the highest value that can be shown by the API test kit. My guess, probably around 8. I realized that I made the mistaken assumption that adding a lot of distilled water would automatically cause the pH to drop. Actually, the pH of distilled or very low TDS water can move easily in either direction, can't it.

 

[regani]

Just adding distilled water alone will not significantly change your pH. It dilutes the acids or bases in your your water, but to have a significant effect you'd have to use e.g. 10x as much distilled water compared to tap. Even with a lot of dilution the pH will only come down to about 7.
You may have to increase the amount of peat and recirculate the water through for a few hours, or store your water over the peat ( some aeration for circulation helps) for a few days to get maximum effect,

 

[skoram]

Yea I was expecting it to go down through the combination of distilled water and peat/leaves - just goes to show how ignorant I still am about water chemistry and blackwater!

Well, in some ways failures are more valuable than successes. Now I know that I should not mix the distilled with much, or any, tapwater, and that I should circulate water more strongly through peat for it to have a significant effect on the pH.

 

[Mike Wise]

My guess is that Seoul 'conditions' its water like here in Denver. We, too, have soft water that by itself is slightly acid. The water department adds a base (NaOH?) to the water to raise the pH so that the water pipes don't dissolve over time. Cycle the water through the peat in a separate vat. You should see the pH drop.