TDS of RO raising in bucket.

[ErtyJr]

Hey guys,
so I'm just starting to get into dealing with TDS and understanding it. Up untill now I have always used PH/GH/KH as a measurement untill I found out how important TDS is and how it can differ from what you would expect.

So anyways, I always get buckets of RO on Sunday morning, and I use the majority on sunday doing large water changes on all my tanks. I save 3 buckets though, and throughout the week, I do 15-25% water changes with pure RO into my "blackwater" tank daily. This tank holds my WC breeding pair of A. sp. abavaxis. I have blackwater in quotes as it is very lightly blackwater, seeing as how I change the water so often.

Now here is my question. When I get my RO it is generally 10-20 TDS, but today is Tuesday, and I measured my RO, it is reading 250 TDS! And the even more odd thing, my blackwater tank which gets a pure RO water change daily, 15-25% has a reading of 110 TDS. How is this RO water shooting up so high while in a bucket with a lid, and then dropping back down when in a light blackwater tank filled with tannins?

Also in blackwater, what is a good tds to aim for when breeding apistogramma that require soft water? In this tank my A. sp. abacaxis female is currently guarding wrigglers. Unsure as to how many as they are inside a log I can not look into, but I assume they are wrigglers now as she has been guarding them 4 days now.

 

[unhappyfeet]

I'm no chemist/ physicist but am also getting into the idea of more accurately controlled water. Here's a few ideas for you to consider, I'm not saying these are definates more over active musings from a dodgy brain! 1.water temperature differences can swing results and exaggerate differences between 2 differing sources, your tank is probably warmer than your home or bucket store.

2. Contamination from your water vessel causing ion reading issues as they transfer from vessel to water
3. Does agitated water read different to still water.

Do you have your own ro machine, you use a lot of water.
Hope these musings help, I'm off to eBay to order a conductivity meter lol

 

[ErtyJr]

I'm no chemist/ physicist but am also getting into the idea of more accurately controlled water. Here's a few ideas for you to consider, I'm not saying these are definates more over active musings from a dodgy brain! 1.water temperature differences can swing results and exaggerate differences between 2 differing sources, your tank is probably warmer than your home or bucket store.

2. Contamination from your water vessel causing ion reading issues as they transfer from vessel to water
3. Does agitated water read different to still water.

Do you have your own ro machine, you use a lot of water.
Hope these musings help, I'm off to eBay to order a conductivity meter lol

1) temperature does affect reading but the meter I have has temp compensation. I got a new bucket of RO yesterday to test side by side, both were fairly similar in temp and one read 14 as the other read 250.

2) this is what I believe is happening but don't know how to change it lol.

3) I don't know, I considered it but I can't see how it would.

 

[unhappyfeet]

're:bucket, are they the same material...plastic or metal, I'm just thinking that the water becomes more ionized when stood, some chemical reaction from the vessel. Once the water is added to the tank these free ions (leeches from the storage vessel ) are displaced by pump agitation or key to something at an atomic level which was suspended in the aquarium.

Or maybe I'm really reaching and stretched the grey stuff here.... My head hurts, must be nap time

 

[gerald]

TDS less than 30 mg/L is just too unstable for aquariums, in my experience. I'd guess 30 to 80 mg/L TDS (50 to 130 uS conductivity) should be a good range for most obligate blackwater species. It really doesn't need to be as low as you'd find in some natural blackwater streams. Blackwater species live where they do because they have an advantage where other species can't live; that doesn't mean they need or "prefer" such extreme conditions. Also, fish in nature can obtain minerals from the substrate (groundwater seeps, benthic bugs and worms) that appear rare or absent in typical water samples taken near the stream or lake surface. In aquaria we dont have nearly as much difference between ion concentrations in the substrate vs in the open water because of diffusion. Also keep in mind that TDS tells us nothing about what the particular ions are, or whether certain important ions are missing. Fish blood and cell fluid salinity is around 1/4 seawater for most teleost fish, regardless of whether they live in Rio Negro, Lake Tanganyika, Devil's Hole, or the Red Sea.

I have no clue how RO water stored in plastic buckets (presumably clean, without old crusty lime scale) could be rising from 20 mg/L to 250 mg/L TDS. That's weird, unless you have salty air.

 

[ErtyJr]

TDS less than 30 mg/L is just too unstable for aquariums, in my experience. I'd guess 30 to 80 mg/L TDS (50 to 130 uS conductivity) should be a good range for most obligate blackwater species. It really doesn't need to be as low as you'd find in some natural blackwater streams. Blackwater species live where they do because they have an advantage where other species can't live; that doesn't mean they need or "prefer" such extreme conditions. Also, fish in nature can obtain minerals from the substrate (groundwater seeps, benthic bugs and worms) that appear rare or absent in typical water samples taken near the stream or lake surface. In aquaria we dont have nearly as much difference between ion concentrations in the substrate vs in the open water because of diffusion. Also keep in mind that TDS tells us nothing about what the particular ions are, or whether certain important ions are missing. Fish blood and cell fluid salinity is around 1/4 seawater for most teleost fish, regardless of whether they live in Rio Negro, Lake Tanganyika, Devil's Hole, or the Red Sea.

I have no clue how RO water stored in plastic buckets (presumably clean, without old crusty lime scale) could be rising from 20 mg/L to 250 mg/L TDS. That's weird, unless you have salty air.

You bring up some good points and information as always gerald.

The reason I add pure RO on a daily basis is because when this tank was set up it was not planned to be blackwater or to house a fish with such software requirements (my WC A. sp. abacaxis). It was meant as a breeding / fry rearing tank for my A. cacatuoides which actually prefer a bit harder but still soft water. So the tank has a lower level of eco complete which has buffering capabilities and is capped with fine grain black diamond blasting sand. The plan was to let the fish settle in and quarantine there for 1-2 months, and then redo substrate with a very fine black diamond blasting sand(inert)

1 week after being in quarantine a day after the first water change they decided to spawn. The eggs were lost as the ph was 6.5 and tds was moderately hard (still fairly soft)

Since then I have been doing water changes every day to keep ph and tds lowered constantly fighting my stupid eco complete, and after 1 week they spawned again. The eggs have made it this time but all that is really not so relevant. But it only raises more questions.

If eco complete has buffering capabilities how is my 250 tds water from the bucket going into this tank and then it becomes 115 or so?

Also as far as salty air, the buckets are all kept closed completely, with the lid on. I can't imagine how they might be becoming contaminated from the air.

I don't know, none of this makes sense to me >.<