Alkaline/Hard water used for water change into acidic/soft water aquarium

[uk_sjo]

As part of my new tank venture, I am intending to re-use an old method I used to use for performing somewhat automatic water changes. I use a sealed container with 'fresh' water and cycle this with tank water. This is a closed loop system with a pump, which ultimately mixes the two together - not the most efficient method, but tap water/dechlorinator is cheap (dodgy diagram below).

This wasn't an issue back in the marine days as the tap water/salt mix was fairly consistent to what was in the tank. Now in my new freshwater planted tank, this is unlikely to be the case due to substrate/system choice.

What problems can using tap water (with seachem prime) for a water change in a soft water tank cause? Appreciate there may be high TDS and some phosphates in the water.

I can do the change/mix cycle over a longer period (e.g. minutes/hours as necessary).

 

[LMuhlen]

If you change water with hard water, your soft water tank will turn into a hard water tank...

 

[uk_sjo]

If you change water with hard water, your soft water tank will turn into a hard water tank...

Well, I will be starting the tank with tap water, and based on the information on this forum (and the marketing spiel on the substrate products), the hardness and ph will drop...

 

[simon_the_plant_nerd]

Well, I will be starting the tank with tap water, and based on the information on this forum (and the marketing spiel on the substrate products), the hardness and ph will drop...

Have you got a local water report? If you fill your tank with tap water and make regular changes with the same tap water you’re very unlikely to see a change that is detrimental to your plants or livestock.

Like in a reef tank, consistency is key.

 

[uk_sjo]

Have you got a local water report? If you fill your tank with tap water and make regular changes with the same tap water you’re very unlikely to see a change that is detrimental to your plants or livestock.

Like in a reef tank, consistency is key.

I don't have a report to hand, but from my reefkeeping days pH was around 7.8 and on the upper end of the hardness. TDS was sometimes over 400!

Youir point about regularity is key - See, I don't have experience of how quickly the substrate is going to modify the water params. Will it soften/drop ph in a day, week, month?.. Of course, 'it depends' no doubt

I liked the KISS method with reefkeeping - Berlin method mostly, avoided hard corals so didn't need a calcium reactor - instead relied on frequent water changes with a decent salt/mineral package, which kept things consistent.

 

[hypnogogia]

The other thing is that the impact of the substrate will reduce over time, so eventually you will end up with a hard water tank anyway. If your water source is hard and you want a soft water tank, the only long term way of achieving that is to use RO or, like I do, rainwater.

 

[uk_sjo]

The other thing is that the impact of the substrate will reduce over time, so eventually you will end up with a hard water tank anyway. If your water source is hard and you want a soft water tank, the only long term way of achieving that is to use RO or, like I do, rainwater.

Yeah. I'm trying to keep this as simple and as easy to maintain as possible, so RO is out of the question. Perhaps i'll only have a minimal amount of active substrate to minimise the swing over time..

 

[Conort2]

Well, I will be starting the tank with tap water, and based on the information on this forum (and the marketing spiel on the substrate products), the hardness and ph will drop...

That won’t last for long, your substrates buffering capacity will soon be exhausted with hard water. The only proper way to have a soft water tank will be to use rain or RO water as mentioned by @hypnogogia

 

[uk_sjo]

That won’t last for long, your substrates buffering capacity will soon be exhausted with hard water. The only proper way to have a soft water tank will be to use rain or RO water as mentioned by @hypnogogia

I'm happy having a hard water tank, i'll stock accordingly. The wife won't be too happy she can't have (happy) neon tetras, but such is life. Perhaps I can find some tank-bred ones in the south east..

 

[simon_the_plant_nerd]

I don't have a report to hand, but from my reefkeeping days pH was around 7.8 and on the upper end of the hardness. TDS was sometimes over 400!

Youir point about regularity is key - See, I don't have experience of how quickly the substrate is going to modify the water params. Will it soften/drop ph in a day, week, month?.. Of course, 'it depends' no doubt

I liked the KISS method with reefkeeping - Berlin method mostly, avoided hard corals so didn't need a calcium reactor - instead relied on frequent water changes with a decent salt/mineral package, which kept things consistent.

While aquasoils can soften water by cation exchange, the effect it will have on your water will be affected by how hard your water is to start off with and how frequently you are doing water changes.

As you will be continuously buffering the water through changes and top offs, it’s unlikely you will see much of an effect, especially as your water is hard already. As you will never “recharge” the substrate so to speak, once it has done all the exchange it is full up and won’t do any more and that will happen quickly in hard water. Your hard water will likely stay hard but if you wanted consistently soft water (using RODI and remineralisers) you may have to watch water parameters more.

What you may be interested in is how well the CEC of the substrate locks up nutrients for later use by plants.

I’m new to the hobby myself so some experts should be along soon to explain better.

EDIT: All the links are broken. I think because I’m on mobile. I’ll try to fix them.

 

[uk_sjo]

As you will be continuously buffering the water through changes and top offs,

Well, i'm equally happy to not do water changes.. but not sure that will be successful (although I am sure some people have proved the point one way or another, perhaps deliberately or accidentally!)..

 

[simon_the_plant_nerd]

I'm firmly in the camp that does water changes. I do them carefully and match water parameters as well as I can. I tried to avoid it on my reefs because salt is expensive but tap water is free where I live so no excuse anymore. 😄 I personally really enjoy water change day now (probably because I keep small tanks) and love seeing the fresh clear water.

 

[uk_sjo]

I'm firmly in the camp that does water changes. I do them carefully and match water parameters as well as I can. I tried to avoid it on my reefs because salt is expensive but tap water is free where I live so no excuse anymore. 😄 I personally really enjoy water change day now (probably because I keep small tanks) and love seeing the fresh clear water.

Yeah, I had enough reef tanks to try both with and without. It really depends on what you're keeping (I guess that's always the number one thing). I had a species tank with a nice Pseudosquilla ciliata (bright yellow mantis shrimp). It was only a cube, but 'Spike' kept the gravel turned over so much that nothing really built up in it, however this tank never had a water change, although auto-top up as it was an open top tank.

 

[Bradders]

I personally really enjoy water change day now (probably because I keep small tanks) and love seeing the fresh clear water.

Amen to that. What was once a burden has now become an almost zen-like moment. (Well, sort of anyway!).

 

[dw1305]

Hi all,

pH was around 7.8 and on the upper end of the hardness. TDS was sometimes over 400!

It will be about pH 8 and 18 dGH and 18dKH for geographical reasons, there is a water hardness map in <"Some handy facts about water"> .

See, I don't have experience of how quickly the substrate is going to modify the water params. Will it soften/drop ph in a day, week, month?.. Of course, 'it depends' no doubt

The other thing is that the impact of the substrate will reduce over time, so eventually you will end up with a hard water tank anyway.

Yes "it depends", just because it is "ion exchange" and that means there are a number of variables, but as @hypnogogia says hard alkaline water will mean that the exchange sites rapidly <"exchange their initial hydrogen (H+)"> ions for calcium (Ca++) ions from the water column.

cheers Darrel

 

[uk_sjo]

It will be about pH 8 and 18 dGH and 18dKH for geographical reasons, there is a water hardness map in <"Some handy facts about water"> .

Yes, you're probably right. I wasn't much of a tester when keeping reefs. I had a TDS meter on my RO unit to check when the filters needed replacing, a pH probe in the tank, and that was pretty much about it. I mostly went by the visible health of the inhabitants!



Well, it looks like i'll end up with a relatively 'hard' tank, even with the substrate. I'm OK with that. I just want predictable, where possible!

 

[dw1305]

Hi all,

I had a TDS meter on my RO unit to check when the filters needed replacing, a pH probe in the tank, and that was pretty much about it. I mostly went by the visible health of the inhabitants!

I like <"inferential techniques">, they don't seem as "scientific" as water testing, but they are equally valid.

Because you have datum values for sea water (and sea water is both uniform and really salty) it actually makes testing somewhat more straight forward. It is also a much more of a black and white scenario than freshwater, where it is all shades of grey.

The problem is that freshwater is much more variable and there isn't much similarity between <"Lake Tanganyika and the Rio Negro">.

Well, it looks like i'll end up with a relatively 'hard' tank, even with the substrate.

I don't see hard water as a deal breaker.

Cheers Darrel

 

[Bradders]

I don't see hard water as a deal breaker.

Agreed. @uk_sjo I have some cardinal tetras in my aquarium, they are not in soft water (Hard / 18dH) and PH is above their 'ideal' range (7.6). They look beautiful, been happy for last 9 months and have grown nicely.

I have been messing around with the water for the last few weeks, taking it softer, achieving a TDS of 140 etc. Nothing changed for the fish. I think the plants have had an uptick though!

 

[uk_sjo]

Agreed. @uk_sjo I have some cardinal tetras in my aquarium, they are not in soft water (Hard / 18dH) and PH is above their 'ideal' range (7.6). They look beautiful, been happy for last 9 months and have grown nicely.

I've read online some opinions/factoids that they'll live 2-3 years in non-ideal water, and maybe another year or two in ideal conditions. Not sure where the data is backing that up though

 

[dw1305]

Hi all,

I've read online some opinions/factoids that they'll live 2-3 years in non-ideal water, and maybe another year or two in ideal conditions. Not sure where the data is backing that up though

I think the issue is <"nephrocalcinosis">. There are scientific papers on salmonids etc.

cheers Darrel