question on water hardness and leaching

[anewbie]

A couple of my aquarium have higher ec than expected and i'm trying to figure out why.

One of them has an ec of around 55 and ph around 6.8; i did an api test this morning and gh was around 3 and kh was below 1; i had presumed that if rock or substrate leached it would be kh and not gh; but what would raise the gh so high. This aquarium does have a different substrate - has been setup for around a year. I'll be taking some of the substrate out putting in a cup with ro water and waiting a week to see if the ec changes (though the plastic on the cup might also leach). This aquarium might have rocks i can't remember - it is a 65 and the fishes in it were said to like caves but it also has a lot of driftwood - mostly Mopani wood and a bit of spider wood.

The 2nd aquarium has the same substrate as a 20 long - it has an ec of around 50 while the 20 long has an ec of 18 (it has been setup for around 4 months while hte 20 long for a year). The only hardscape in this aquarium is mopani wood though it has a lot of leaves and plants - so again i'm not sure why the ec would be so high.

Thoughts/suggestion of what to look into ?

This is a picture of the 2nd aquarium since i have it handy - initially i was using it to test growing plants in blackwater but later added the a. ladisalo pair (female wants to spawn but male seem to snub her)

 

[MacZ]

i had presumed that if rock or substrate leached it would be kh and not gh

Na, usually both, and keep in mind KH is part of GH. So the Mg/Ca-part of the GH is only 2° + 1° Carbonates.

I'll be taking some of the substrate out putting in a cup with ro water and waiting a week to see if the ec changes (though the plastic on the cup might also leach).

Take a drinking glass. Those are sure to not leach.

so again i'm not sure why the ec would be so high.

Remember, EC is just the sum of ions in the water. So things like Nitrates do add up o the EC too. My tank was at a constant 45µS/cm by the end and there was a lot of organic stuff in the water. Even H+ ions in very acidic water add on the EC.

 

[anewbie]

Na, usually both, and keep in mind KH is part of GH. So the Mg/Ca-part of the GH is only 2° + 1° Carbonates.


Take a drinking glass. Those are sure to not leach.


Remember, EC is just the sum of ions in the water. So things like Nitrates do add up o the EC too. My tank was at a constant 45µS/cm by the end and there was a lot of organic stuff in the water. Even H+ ions in very acidic water add on the EC.

So do you think a rock would raise the gh to 3 without impacting kh ?

 

[MacZ]

No, usually rocks and substrate raise to a saturation point. You would end up at about 8-10.

 

[anewbie]

No, usually rocks and substrate raise to a saturation point. You would end up at about 8-10.

Might be the water changes keeping it under control - anyway I'll start my substrate test tuesday and run it for a few weeks.

 

[Mazan]

I don't know the answer, but I have noticed that my two tanks with rocks in have slightly higher conductivity than those with only wood. It is not a big difference (TDS in the 20s in wood only tanks but in the 30s in those with rocks). The rocks come from my local river which has very soft water, but not quite as soft as rainwater. I thought at first it was due to the higher stocking in the Guianacara tank, which has rocks, than the others, but it was the same when I set up a new rocky tank, even before I added any fish.

Having said this, a few years ago I had a similar situation in another 180l tank that had no rocks but always had slightly harder water and higher pH than the tap water or the other tanks, I never knew the reason.

 

[anewbie]

For the record i started the test yesterday (Feb 18) @ 11 am cdt tds 16:
Today (Feb 19) @ 10 am cdt tds 17;
(I won't measure it every day but i will update it once or twice during the next two weeks); mostly this comment means i won't have to totally work off of memory

 

[dw1305]

Hi all,

For the record i started the test yesterday (Feb 18) @ 11 am cdt tds 16:
Today (Feb 19) @ 10 am cdt tds 17;

Those are very low values, you basically have very few ions of any description. The actual ppm TDS value would be higher, but <"difficult to measure">.

cheers Darrel

 

[Mazan]

I am now getting similar readings in the dwarf pike tank that I have been trying to convert to blackwater, I have just been using rain water for water changes, today TDS is reading 15. Actually I just tested my tap water again and it is also 15, I think that is because its been raining so much lately, its normally only around 20 anyway. The rainwater seems to measure 10-12.

 

[Mike Wise]

Please realize that you are adding minerals to the water every time that you feed your fish. Additionally rainwater does absorb minerals while falling through the air. Unless you have continuous flow through a tank, like a stream does in nature it is unlikely to achieve similar water values found there.

 

[anewbie]

Well today it was ec 26 so i guess it is leaching; of course the substrate to water ratio in the cup is higher than the aquarium but still ... i can't tell how bad this is but i'll give it one more week.

 

[Ben Rhau]

Is the substrate directly from the tank, or new from the bag?

 

[anewbie]

From the tank; i do have a new bag that i will eventually open but if there is 'stuff' in the substrate leaching i would expect it to reach quick equilibrium.

 

[Mazan]

Well today it was ec 26 so i guess it is leaching; of course the substrate to water ratio in the cup is higher than the aquarium but still ... i can't tell how bad this is but i'll give it one more week.

Well if before the TDS was 17 at that point the EC must have been higher than 26, so it has become lower not higher? Unless I am missing something?

 

[anewbie]

Well if before the TDS was 17 at that point the EC must have been higher than 26, so it has become lower not higher? Unless I am missing something?

I don't follow you - I measured 17 and yesterday i measured 26 so it raised from 17 to 26 sitting idle in the cup for a ~week.

 

[MacZ]

I don't follow you - I measured 17 and yesterday i measured 26 so it raised from 17 to 26 sitting idle in the cup for a ~week.

And you took the sand from your tank. I'd expect this to be the result of biological activity, not of minerals dissolving into the water. That would have brought much higher rises.

 

[anewbie]

And you took the sand from your tank. I'd expect this to be the result of biological activity, not of minerals dissolving into the water. That would have brought much higher rises.

Could be but not sure how i can measure the 'biological' activity. Still i will see what happens in another week

I suppose i could open a fresh bag and get some out of it before doing something drastic like tearing down the aquarium to replace the substrate.

 

[MacZ]

You could simply confirm the presence of GH and KH as indicators of leaching of anorganic sompounds.

 

[anewbie]

You could simply confirm the presence of GH and KH as indicators of leaching of anorganic sompounds.

I'm not sure i could measure gh or kh at ec 26 (tds 13).

 

[Mazan]

I don't follow you - I measured 17 and yesterday i measured 26 so it raised from 17 to 26 sitting idle in the cup for a ~week.

Ah OK you said TDS 17 and EC 26, they were both TDS then?