blackwater tank cycling?

[anewbie]

Sadly i'm setting up my first true blackwater tank - i wanted to ask about cycling/when it is safe to add fishes. The aquarium has been running for 4 weeks without stocking. I've not yet taken the ph (which i will do in about 8 days after i move into the house); the tds has been sitting around 25 - is it actually safe to add a few fishes or do i have to do anything special to cycle in such low ph. I know that low ph will make ammonia less harmful for fishes but not if that means it is totally safe.

 

[MacZ]

Ammonium changes to significant percentages ammonia at a pH far above 7, so this isn't a problem at all. But there is another thing to consider: Nitrite, which is especially dangerous at low pH.
But the nitrogen cycle also tends to leave out the nitrite stage in these conditions.

It takes months until a softwater tank is fully developed. I avoid the word cycled, as I don't think a tank like this is ever cycled in the sense the word is usually used.

How much organic material have you added? How much leaf litter, how much wood or peat? That will determine how much bioload the tank can already take.

 

[anewbie]

Ammonium changes to significant percentages ammonia at a pH far above 7, so this isn't a problem at all. But there is another thing to consider: Nitrite, which is especially dangerous at low pH.
But the nitrogen cycle also tends to leave out the nitrite stage in these conditions.

It takes months until a softwater tank is fully developed. I avoid the word cycled, as I don't think a tank like this is ever cycled in the sense the word is usually used.

How much organic material have you added? How much leaf litter, how much wood or peat? That will determine how much bioload the tank can already take.

The aquarium is stuff full of driftwood with some of it floating; there is a bag of peat (300g) in a bag in the sump; there is approx 50 medium size catappa leaves; all of this for a 48x30 (in) or 122 x 76 (cm) area for the past 4 to 6 weeks (i forget the exact date i dumped it all in approx 3 to 4 weeks ago).

 

[MacZ]

Allright. Check for Nitrite. If there is none detectable, it's safe.

 

[Mike Wise]

I'm old school (maybe because I'm old?), but to me no fish = no biological filtration. I treat blackwater tanks like I do tap water tanks. Introduce a couple of hardy blackwater fish, wait a week and if everything looks good, then add a couple more. Then check NO2 and NO3 levels. If OK, partial water change and add a couple more fish if you want. If nitrogen levels are good after 5 - 6 week, then feel safe adding apistos.

Now it's simpler for me. I run a sponge filter in an established blackwater tank (and stir up bottom sediment). After a couple of days I move the filter to the new tank along with the fish.

 

[Ben Rhau]

I'm new school. I think you can add fish as soon as you see healthy plant growth, as long as you're not overstocking and have a lot of plants including floaters. I assume you have plants, judging from your other tanks? That actually takes some time, because most plants experience a bit of shock when transferred tanks with close to zero nutrients.

I also recommend stabilizing your pH before starting the clock. Let's say you "cycle" the tank at pH 6.5, and then drop it to pH 4. Your flora aren't selected for that pH.

For me, it took a while to figure out how to get my parameters stable at a low pH (it kept wanting to rise). So I didn't add fish for about 8 weeks (maybe more, because I was lazy). I did add a very small amount of fish food, but I'm not sure that was completely necessary. I waited until the plants were happy and I saw detritus worms, copepods, ostracods.

Allright. Check for Nitrite. If there is none detectable, it's safe.

I never saw a nitrite spike, which is anecdotally somewhat common in blackwater tanks.

-B

 

[MacZ]

I never saw a nitrite spike, which is anecdotally somewhat common in blackwater tanks.

I know, me neither, but rather safe than sorry, eh?

I also recommend stabilizing your pH before starting the clock. Let's say you "cycle" the tank at pH 6.5, and then drop it to pH 4. Your flora aren't selected for that pH.

Important point. I forget mentioning that sometimes as it's a given to me.

 

[Ben Rhau]

Important point. I forget mentioning that sometimes as it's a given to me.

Yup, I only mentioned it bc anewbie said he hasn't measured pH yet.

 

[anewbie]

I'll measure ph also i will order some cheap kubotai rasbora - i think they can take blackwater

 

[MacZ]

kubotai rasbora - i think they can take blackwater

Species from Myanmar and Thailand are rther hardwater.

 

[anewbie]

Species from Myanmar and Thailand are rther hardwater.

Not according to description on seriously fish - i will quote:

Brevibora dorsiocellata – Eyespot Rasbora (Rasbora dorsiocellata) — Seriously Fish

www.seriouslyfish.com

---
Native to southern Thailand, Peninsular Malaysia and the Greater Sunda islands of Borneo and Sumatra. Type locality is ‘Muar River, Tebinh Tinggi, Johore, Malaysia’.

In Peninsular Malaysia localities include the Selai and Muar rivers in Johor state and the blackwater swamp lake of Tasek Bera in Pahang state while in Sumatra the only report we’ve been able to find seems to refer to the Lalah River, Riau province in the east of the island.
---
Temperature: 20 – 25 °C

pH: The widely available, captive-bred fish are quite adaptable and should be happy within the range 5.0 – 7.5. If you have the opportunity to purchase wild specimens they are likely to do best on the acidic side of neutral.

Hardness: 18 – 179 ppm
--
(i said kubotai which has similar description on seriously fish but since these were less expensive they are the ones i ordered):
--
You might be correct and hte info on seriously fish incorrect but one of you is not correct (I think)

 

[MacZ]

Type locality beats catch localities. Stick to what they say.

 

[anewbie]

Type locality beats catch localities. Stick to what they say.

That was too cryptic for my poor brain; you mean location where i am buying them or what seriouslyfish sez or something else ?

 

[Ben Rhau]

I think Mac is saying to listen to seriouslyfish.

Why not just start with the schooling fish that you're planning to add? (e.g., tetras, pencil fish, etc.) Whether you do that or add kubotai rasbora, an extremely low bioload won't cycle your tank. They'll be more of a canary to determine whether the water is habitable.

 

[anewbie]

I think Mac is saying to listen to seriouslyfish.

Why not just start with the schooling fish that you're planning to add? (e.g., tetras, pencil fish, etc.) Whether you do that or add kubotai rasbora, an extremely low bioload won't cycle your tank. They'll be more of a canary to determine whether the water is habitable.

Because i'm going to go with marbel hatchet fishes and red pencil fishes - shipping for those two speices (from different vendors) is around $50 plus cost of fishes. I can get the rasbora for $30 + $12 shipping from aquahuna - i rather spend $40 to test the aquarium than $250 to test the aquarium.
-
The total load won't be that high for the volume of water in the end. I think i'm planning on 18 pencil; 20 hatchet and 8 bitatiana (sp) in ~100 gallons of water.

 

[Ben Rhau]

Yeah, thought that might be the case. Makes sense.

 

[anewbie]

I'm having a bit of problem; if the ph probe i am using is accurate the ph is staying around 6.6; the tds has remained around 25 and there is a ton of decaying catapaca leaves and some peat in a filter bag in the sump. The leaves and peat have been in there since early sept so at least 2 weeks probably closer to 4. Shouldn't the ph be dropping ?

 

[Ben Rhau]

6.6 does seem high, but it general I've found that if I start with TDS 0, I can't keep the pH below 5 without using acid (I don't use peat anymore). Pure distilled water will stabilize around pH 5.5, because dissolved CO2 will generate KH (via the carbonate - carbonic acid equilibrium). Given that you're starting with TDS 25 and not TDS 0, I have to conclude that the ions in your water are contributing to KH. In terms of what you're adding to acidify:

• Leaves won't affect the pH much.
• Peat will lower the pH, but it's hard to predict by how much because peat isn't uniform, and it can be exhausted. My guess is that there isn't enough relative to your volume of water.

I'm always dumbfounded when I hear people warn that low TDS tanks are subject to pH crash. I want the pH to stay low, and it takes work to figure out how.

-B

 

[anewbie]

6.6 does seem high, but it general I've found that if I start with TDS 0, I can't keep the pH below 5 without using acid (I don't use peat anymore). Pure distilled water will stabilize around pH 5.5, because dissolved CO2 will generate KH (via the carbonate - carbonic acid equilibrium). Given that you're starting with TDS 25 and not TDS 0, I have to conclude that the ions in your water are contributing to KH. In terms of what you're adding to acidify:

• Leaves won't affect the pH much.
• Peat will lower the pH, but it's hard to predict by how much because peat isn't uniform, and it can be exhausted. My guess is that there isn't enough relative to your volume of water.

I'm always dumbfounded when I hear people warn that low TDS tanks are subject to pH crash. I want the pH to stay low, and it takes work to figure out how.

-B

Should i add acid for the boot strap; if so what type ? Is my spit acidic enough; do i need a cobra that spits acid ? There is a devil-rider stick insect that has an acid spit. Hum.... not sure what to do here.

 

[Ben Rhau]

I would. It would either make your peat last longer or make it not necessary at all. It will make the pH a lot more predictable. Any strong acid will do. Cobra venom sounds great. I use phosphoric acid, but if you can't find that, "API PH Down" is 9.6% sulfuric acid and pretty easy to buy in small volumes. Test it outside the aquarium to understand how many drops you need to add per gallon to your incoming water to get the pH to where you want it.

The tank pH will want to rise, so I would:

• Assuming there are no animals in the tank, first get the tank to a desirable pH, maybe just 10 drops or so at a time.
• Water change with water at the correct pH.
• Measure your tank pH for the next few days. It will rise for a few days. You'll likely need to add more acid to your incoming water until you reach a point where the pH is stable in between water changes. It will always want to rise if you go longer than that.

It took me a few weeks maybe to get it to where I know exactly how much acid to add to my incoming water. Once your pH is stable, then look at new plant growth starting on that date and decide when you're comfortable adding your canary animals.

Good luck!