Hardness increasing

[WhistlingBadger]

This is weird. My tap water is soft, usually 4 degrees GH or less. Today I checked the hardness of my Sumatra tank, something I admittedly don't check that often, and it was 12 degrees! What on earth!? This could explain why some of my fish--black-water species all--haven't been doing so well.

 

[WhistlingBadger]

I guess my water changes--about 15% each week--aren't enough to keep up with the hardness increase from evaporation? Water is pristinely clean--nitrates don't even register. It never occurred to me that hardness might be increasing. Time to dig out a bigger bucket, I guess.

 

[Back in the fold]

How in the world can your water be soft in the limestone capital of the Rocky Mountain West?

 

[Naughts]

Did you re-check the tap water GH? It can change.
Do you have a tank lid?

 

[Byron]

You need to eliminate possibles. Does the source (tap) water go through any sort of filtering, like a softener, or household filter of some sort? Is there a substrate that may be leeching minerals, not only a calcareous but a plant enriched? Are you adding any sort of plant additive/fertilizer? Any substances going in the tank, thinking of water adjusters, buffers, etc?

 

[WhistlingBadger]

Good questions, all. Source water is currently 4 degrees GH. Slightly alkaline pH, but very soft. We do have a great deal of limestone, so it's a mystery to me why the water is so soft, but it is. I've never seen the tap water here measure over 4 degrees; sometimes as low as 2. This is true in several different sources around town, and has remained so over many years.

I don't have a water filter or softener of any kind at my house.

Substrate is organic potting soil under black blasting sand. No fertilizers or calcareous additives in the soil, and this substrate has been in the tank for two years.

I don't add any plant additives/fertilizers to the water or soil. The only substance added to the tank is Seachem Prime to dechlorinate during water changes. And a variety of fish food, of course: Flakes, freeze dried tubifex, frozen brine shrimp, the occasional fruit fly.

Strange, isn't it? The only thing I can think of is that my water changes are too small, not enough to keep up with evaporation. But I'm not sure that explains something this extreme.

 

[WhistlingBadger]

And yes, the tank is covered. It has a few small openings for emergent plants to grow through.

 

[kiko]

I guess my water changes--about 15% each week--aren't enough to keep up with the hardness increase from evaporation? Water is pristinely clean--nitrates don't even register. It never occurred to me that hardness might be increasing. Time to dig out a bigger bucket, I guess.

I would check the tap-water first...as more often than not, things change and people just get caught unprepared
and also the reason why some don't even risk tap and just go with something they can control like remineralized RO water

 

[Byron]

I concur on the tap water. Retest, but also check with the water authority and see what they give as the GH and KH (Alkalinity), and pH while you're at it. It is always possible that your tests are off for some reason so this will confirm or not.

I have always read that insufficient water changes are more likely to result in a diminishing of minerals, not increasing. Water changes replenish the minerals, here calcium and magnesium, that fish and plants are using. I have always though too much was made of this, because the amount of calcium and magnesium used by even a tank full of fish and plants will not be much, though with low levels to begin with I suppose they might become depleted. And while it is true that evaporating water will leave behind the calcium and magnesium, with water this soft I can't see that really being an issue. I would not insist upon this though, should others have a contrary view. But regardless, the only explanation of increasing GH with minimal water changes would be a source of calcium and/or magnesium from somewhere.

You said you are not adding any substances; my reason for asking this was that years ago I added magnesium sulphate, epsom salts, just a spoon or so for the plants. This was back in the 1980'sand the author of the planted tank column in FAMA recommended this. It certainly did improve the plants' growth some, though at the time I was ignorant of the possible effect on my soft water fish. I had water out of the tap that was zero GH/KH and pH was below 5.

 

[StevenF]

Good questions, all. Source water is currently 4 degrees GH. Slightly alkaline pH, but very soft. We do have a great deal of limestone, so it's a mystery to me why the water is so soft, but it is.

Limestone dissolves very well in acidic water but poorly in when the PH is very close to 7. Above aphof7.5 the the solubility's very low, near zero. IF the water is from a lake or stream it will have a low GH. IF it comes from a well the GH can be a lot higher depending on how much CO2 or other acids are in the underground aquifer. So a 4 degree GH is not unusual with a lot of limestone pressent in the environment.

Your problem is likely due to insufficient water changes. However some water utilities do switch from surface water the well water during the dry season or droughts. So in some places it can change a lot between summer and winter. Yes plants will consume Calcium and magnesium, They are necessary for grrowth. 3 times more calcium than magnesium is generally required for good growth. in most water sources calcium dominates and very little magnesium will be pressent. So even in medium to high GH levels magnesium deficiency is possible.

 

[WhistlingBadger]

I tested my tap water just today, with two different test (API GH and strips). Both the same results and consistent with the results I've had over the years. I don't see any reason to think that's it.

 

[WhistlingBadger]

Limestone dissolves very well in acidic water but poorly in when the PH is very close to 7. Above aphof7.5 the the solubility's very low, near zero. IF the water is from a lake or stream it will have a low GH. IF it comes from a well the GH can be a lot higher depending on how much CO2 or other acids are in the underground aquifer. So a 4 degree GH is not unusual with a lot of limestone pressent in the environment.

Your problem is likely due to insufficient water changes. However some water utilities do switch from surface water the well water during the dry season or droughts. So in some places it can change a lot between summer and winter. Yes plants will consume Calcium and magnesium, They are necessary for grrowth. 3 times more calcium than magnesium is generally required for good growth. in most water sources calcium dominates and very little magnesium will be pressent. So even in medium to high GH levels magnesium deficiency is possible.

Our municipal water comes from a creek that leaves the mountains only a few miles from here, so your explanation makes sense. All my plants are growing very well--no sign of deficiencies that I can see.

 

[JuiceBox52]

What substrate do you have? Have you added any new rocks?

 

[WhistlingBadger]

What substrate do you have? Have you added any new rocks?

Black sand with a layer of organic potting soil under it.

 

[JuiceBox52]

Black sand with a layer of organic potting soil under it.

Hmmmm you have a tricky case indeed