How to adjust GH when topping off? I'm confused!

[Courtneybst]

Hey everyone,

I have a query that I couldn't find an answer for from the search.

For the last 6 months I have been keeping a mixed shrimp colony of Neocaridina and Caridina, both happy and breeding. I recently moved them to a slightly bigger, botanical method tank but towards the end of their time in the first tank I noticed several random deaths (particularly the adult crystals). I'm not sure if it's the reason but turns out my GH was super low, like 1 or 2! I wonder if this was causing failed moults...I originally set the tank up with a KH of 2 and GH of 6, but did top offs only so obviously the livestock/plants are consuming the dissolved minerals, but the carbonate hardness didn't shift at all.

My question is, how do I go about bringing the GH back up to 6 when it drops, through top offs? I don't know how much water has evaporated when I top off so how do I calculate how much remineraliser (Salty Shrimp GH+) to use and how much water to add? Is there a really obvious answer staring me in the face or is it's bit more complex, hence my confusion?

One thing I did consider was to fill the tank to the desired level at a GH of 6 and then remove for example 1L and mark the level on the glass. That way I know that 1L has evaporated and can calculate how much salt I need to use based on the remaining water volume. Even this seems complicated to me though!

Cheers

 

[Hanuman]

My question is, how do I go about bringing the GH back up to 6 when it drops, through top offs? I don't know how much water has evaporated when I top off so how do I calculate how much remineraliser (Salty Shrimp GH+) to use and how much water to add? Is there a really obvious answer staring me in the face or is it's bit more complex, hence my confusion?

Replaced evaporated water does not require being remineralized. However WC water does.
Were you using RO water in that tank? or TAP? If RO then simply remineralize the WC volume to the desired GH/KH. If Tap water then I guess depending on the level of Ca/Mg in there you would want to either add some Ca/Mg if water is too soft or cut it with RO if water is too hard.

 

[dw1305]

Hi all,

My question is, how do I go about bringing the GH back up to 6 when it drops, through top offs? I don't know how much water has evaporated when I top off so how do I calculate how much remineraliser (Salty Shrimp GH+) to use and how much water to add? Is there a really obvious answer staring me in the face or is it's bit more complex, hence my confusion?

No, I don't think there is a simple answer.

I'd try using a <"conductivity datum"> (just a range of values where both shrimp types look happy). If you just had Cherry shrimps you could use tap water as your remineraliser, but if you want to <"decouple dGH and dKH"> you need to use an alternative to calcium carbonate (CaCO3).

I'm assuming you are adding magnesium sulphate (MgSO4.7H2O) with your fertiliser, so you could possibly use CaCl2.nH2O as your calcium (Ca++) source and a smaller amount of tap as your dKH source?

If you wanted to avoid tap water all together, potassium bicarbonate (KHCO3) <"would be an option">. The advantage of potassium bicarbonate and calcium chloride is they are used in cooking and you can buy them as "food grade" cheaply and easily.

cheers Darrel

 

[Wookii]

I'm not sure if it's the reason but turns out my GH was super low, like 1 or 2! I wonder if this was causing failed moults...

That would seem likely - did the dead shrimp have the typical band suggesting a failed moult?

My question is, how do I go about bringing the GH back up to 6 when it drops, through top offs?

The mineral content shouldn’t be reduced through top offs with RO water.

I would just monitor your GH levels periodically with a decent titration drip test kit, and add some more Salty Shrimp if and when needed.

Personally I wouldn’t bother adding any carbonates (not sure if you have Salty Shrimp GH+ or the GH/KH+ product), as a zero KH will enable you to keep a lower pH with your botanicals.

 

[Courtneybst]

Replaced evaporated water does not require being remineralized. However WC water does.
Were you using RO water in that tank? or TAP? If RO then simply remineralize the WC volume to the desired GH/KH. If Tap water then I guess depending on the level of Ca/Mg in there you would want to either add some Ca/Mg if water is too soft or cut it with RO if water is too hard.

That's just it, I wasn't doing water changes, only top offs with RO water. I was treating that tank more like a pond than an aquarium since around 70% of the volume was pure plant mass.

Once topped off the KH always measured 2 but the GH is what would fall over time.

I'm assuming you are adding magnesium sulphate (MgSO4.7H2O) with your fertiliser, so you could possibly use CaCl2.nH2O as your calcium (Ca++) source

I was adding fertiliser very sparingly so maybe I should add it more regularly to ensure MgSO4.7H2O is being added. Also I think using Calcium Chloride Monohydrate as you said, would be useful in this scenario. I guess it's just a case of adding a bit a testing?

 

[Courtneybst]

That would seem likely - did the dead shrimp have the typical band suggesting a failed moult?

In fairness I didn't inspect them that well, I just noticed the deaths but I will keep an eye out if I notice it again in the new setup.

The mineral content shouldn’t be reduced through top offs with RO water.

Sorry I worded this weirdly. What I meant was how do I bring the GH back up using top offs.

I would just monitor your GH levels periodically with a decent titration drip test kit, and add some more Salty Shrimp if and when needed.

Probably the most likely solution! I have the Salty Shrimp GH+ currently. Would you just add a little bit and test again? And then repeat until I reach the desired GH?

 

[Hanuman]

That's just it, I wasn't doing water changes, only top offs with RO water. I was treating that tank more like a pond than an aquarium since around 70% of the volume was pure plant mass.

Ca/Mg was consumed through time by plants and shrimps thus reducing GH.

I have the Salty Shrimp GH+ currently. Would you just add a little bit and test again? And then repeat until I reach the desired GH?

Yeap. I would do that. Read the bottle sticker. It should tell you how much you need to add for X volume to reach an X amount of GH.

 

[dw1305]

Hi all,

Ca/Mg was consumed through time by plants and shrimps thus reducing Calcium and Magnesium content in the water.

That one. I'd guess that the magnesium (Mg) is relevant to the plants, but probably much less relevant to the shrimps.

I guess it's just a case of adding a bit and testing?

Probably the most likely solution! I have the Salty Shrimp GH+ currently. Would you just add a little bit and test again? And then repeat until I reach the desired GH?

I'd just use the <"conductivity meter">, you know the value it gives you as correct, with all the chemical tests (like your dGH test) there is more ambiguity.

The great advantage of the conductivity datum is that if your tap water changes, or you don't know how hydrated your salt is, it doesn't matter you just need to keep the conductivity reading in the <"goldilocks zone">.

You can actually work out the amount of dGH (as mg / L Ca++) you've added from the calcium chloride addition. If you want to be entirely sure about the number for the water of crystallization, you would need to heat it and use it as <"anhydrous"> or you could just assume that it is the <"hexahydrate (CaCl2.6H2O)">. Personally <"I'd do the latter">.

cheers Darrel

 

[Courtneybst]

I'd just use the <"conductivity meter">, you know the value it gives you as correct, with all the chemical tests (like your dGH test) there is more ambiguity.

Thanks Darrel!

 

[Wookii]

Would you just add a little bit and test again? And then repeat until I reach the desired GH?

Yeap. I would do that. Read the bottle sticker. It should tell you how much you need to add for X volume to reach an X amount of GH.

☝🏻 What @Hanuman said - just calculate any required addition.

 

[Wookii]

I'd just use the <"conductivity meter">, you know the value it gives you as correct, with all the chemical tests (like your dGH test) there is more ambiguity.

Darrel, would the fact that Courtney is running this as a blackwater tank, and will continuously be adding botanicals and other items to increase water colouration, combined with the minimal/infrequent water changes, not create an upwards movement in conductivity over time potentially masking a decreasing GH (being used here as a proxy for calcium levels)?

 

[dw1305]

Hi all,

would the fact that Courtney is running this as a blackwater tank, and will continuously be adding botanicals and other items to increase water colouration, combined with the minimal/infrequent water changes, not create an upwards movement in conductivity over time potentially masking a decreasing GH

I think it would. @Courtneybst would need to change enough water (with RO) to keep within the "goldilocks zone".

The <"botanicals will add ppm TDS">, but make very little difference to the conductivity, because humic, fulvic and tannic compounds don't carry an electrical charge. Acids add some conductivity, because they are <"H+ ion (proton) donors">, but it is a relatively minor contribution from weak acids.

It is slightly different for me, because I use tap as my remineraliser and rain water as my base water, but I'm a <"fairly fanatical water changer">, I only change a small volume, but on a very regular basis.

When I started keeping fish, I didn't understand the requirement for water changes, <"generally aquarists were wary of changing water"> and fish like Discus were regarded as "extremely difficult to keep". There are still issues with Discus keeping, but water quality is much less of an issue than it was before Discus keepers changed more water.

cheers Darrel

 

[Hanuman]

Darrel, would the fact that Courtney is running this as a blackwater tank, and will continuously be adding botanicals and other items to increase water colouration, combined with the minimal/infrequent water changes, not create an upwards movement in conductivity over time potentially masking a decreasing GH (being used here as a proxy for calcium levels)?

I believe tanins are not electrically conductive hence a TDS meter would be blind to them.
Dammm, Darrel beat me to it.

 

[dw1305]

Hi all,

Dammm, Darrel beat me to it.

It is usually the other way around, I'm writing a considered, or long-winded and irrelevant reply, (delete as appropriate) and some-one posts all the important bits in about four words while I'm still writing.

cheers Darrel

 

[tam]

You can guess what your water is currently made up of and add the corrisponding amount of saltshrimp to bring it to your required level (I'd suggest doing that gradually) the same way you'd remineralise. However, long term you'd probably be better doing a small water change now and then. We put food/ferts/botanicals in and take plants (trimmings) out, but that doesn't mean they balance each other out. The make up of what goes in and what comes out can be different or even just bound up in something, water changing helps reset. I'll put my hands up to not doing huge changes, but a little bit now and then is helpful.

 

[MichaelJ]

Ca/Mg was consumed through time by plants and shrimps thus reducing GH.

Thats it I think.

I believe tanins are not electrically conductive hence a TDS meter would be blind to them.

And this one too... I use botanicals in my shrimp tank as well, and haven't noticed any upward drift in TDS. I dont use a huge amount of botanicals and do WC's fairly often so that may cancel out any TDS creep.

Cheers,
Michael

 

[MichaelJ]

Hi all,

It is usually the other way around, I'm writing a considered, or long-winded and irrelevant reply, (delete as appropriate) and some-one posts all the important bits in about four words while I'm still writing.

cheers Darrel

... even when replies overlap prior posts, there are usually some very valuable high order bit of info in your posts and references that provides more in-depth color to a topic... Not sure how you keep track of all those posts and references though - I cant even remember what I posted yesterday

Cheers,
Michael

 

[Hanuman]

Well it’s a fact that @dw1305 is Gandalf the White while we are mere mordor’s trolls or Hobbits depending what side of the story you fancy to be in.