Problems with pH, fish dying

I have a 15g Fluval Flex aquarium, heavily planted, cycled, with 7 guppies. When I first started stocking the tank (~1mo ago), the tank pH was 6-6.5 (we have a whole-house water softener, and the pH runs low). GH in all my tanks (I have 3), is usually 30, KH ranges between 40-80. Last week I mentioned the low pH to one of the employees at my local fish specialty store. Two guppies had died in the past two weeks, and since my parameters have been 0/0/10, the employee thought the pH might be too low. She recommended I put a rock in the tank to help raise the pH. I don’t remember the name of the rock, but it was in the saltwater section, yellowish, and she called it a lace-something? I bought a medium-sized piece and added it to the tank a week ago. This morning, my pH is 7.8; GH 30, KH 80, ammonia 0, nitrite/nitrate 0/5. I removed the rock from the tank, but I am concerned about crashing the pH. Any recommendations?
Edit: I do a 3g partial water change weekly, which I did this morning.

 

Put the rock back in. The rock is buffering your water and raising the pH making it more hospitable for guppies. You got some good advice to put this rock in the tank. Let it do what it does. It will make your water harder, raise and stabilize the pH at 7.8 and add some minerals (Calcium) for your hard water fish (guppies).

 

A GH of 30 is very low for guppies, they will continue to die.



This chart recommends more than double that GH , between 100 - 200 ppm for guppies. Ether you get some or all of the replacement water from an outside tap before the house water softener or you start adding some African cichlid mixture of minerals.

 

Thank You, I will put the rock back in & look into the minerals for cichlids.

 

Water Softeners are usually a chemical method of lowering GH, KH and pH, the rock will work to bring up the pH, but it won't fix the GH and KH low levels and you'll need at least the mineralization for livebearers for good development.

you can give up on the livebearers though and go with soft water species fish that will enjoy the parameters you have though.
Tetras, Barbs, Gouramis, Corydoras catfish and Angelfish. angelfish are out with a 15 gallon..,.. so are gouramis, unless dwarf.

Apistogramma, Mikrogeophagus, Dicrossus, Nannacara, maybe. I'd need to check the maximum sizes.

Tetras, neons or cardinals even , you could probably do, and no rock and no playing with your water. you'd need to check TDS with a TDS meter and check the sodium. salinity I think though first to be sure of what you have.
the modern softeners usually are less chemical and function off ion exchange and remove Calcium and Magnesium ions in the water and replace them with sodium ions from salts. if it's doing a lot, then there's a lot of sodium ions you aren't testing for that are going into the water, maybe too much.

Naturally soft water typically contains between 10 to 50 parts per million (ppm) of sodium.
typical softened water has 12.5mg of sodium per 8oz glass or Less, or 53mg per liter or less, (53ppm top end unless the water is REALLY hard.) so softened water is just a bit out of the high range of sodium that would occur naturally with soft water.... typically. . but depends on the softener and the condition of the water being softened.

If it's HIGH sodium left over, this is where Reverse Osmosis (RO water) comes into play, to remove what's left and that sodium of softened water. but then you'd need to remineralize to an extent.

there's a hydrometer for testing, there's digital hydrometers, there's test strips also for water testing to see how much sodium is left behind from the softener. it's good to know anyways if you drink it, but I'd think you want to nail down what exactly you are dealing with to figure out the best course of action.

I don't think fighting the water you have every water change is a good idea for the long term and stability just to keep hard water fish, but that's my personal opinion. you likely can do soft water fish, and even the harder ones a lot of people have trouble with, with little to no tweaking to the water and maybe no difficulty, once you know what exactly you are dealing with with your softened water.

 

Water softeners replace the minerals with sodium ions. Is there any way you can bypass the water softener for your water change water? That would take care of your problem.

 

Water softeners replace the minerals with sodium ions. Is there any way you can bypass the water softener for your water change water? That would take care of your problem.

it would depend on how hard and the cause of the hard water though. it might take care of the problem, it might take a mix of bypass, and softened water.....
Like my irrigation water is on well, this is so full of iron, it's ok I guess for grass, it kills fruiting plants though, and even my grass is mostly weeds or centipede grass. Stains my house a nice shade or red/brown where the sprinklers hit that I have to clean off every month also. My city water is fine, that irrigation water from the well I can't even use it in my pool because of the staining it will cause to the surfaces. I'd never dream of putting that in an aquarium.

 

I can’t bypass the softener. I think I will look into some other types of fish, like tetras. Thank you all for your input.

 

What about your outside faucets? They're generally not connected to the water softener. Get a bucket and fill it with the outside water and bring it inside for your WC. Water softeners cause problems with even soft water fish. I breed Discus and Rams so I know a lot about water.

 

Water softeners cause problems with even soft water fish.

Yep.

Depending on the exact resin or salts. Usually only GH (hardness as defined by washing machine manufacturers) is targeted.
KH may be raised unbelievably instead. I have seen results of input GH 15° and KH 11°, with a result of 2° GH and 19° KH. This raises pH accordingly into very uncomfortable values for softwater fish such as tetras.
Some chemicals used lower both GH and KH but raise conductivity. E.g. 17° GH and KH of 16° with a conductivity of 800µS/cm, lowered to 3° each for GH and KH but a conductivity over 1200µS/cm and sodium or potassium levels through the roof. Such a case would still be bad for softwater fish.

 

it would depend on how hard and the cause of the hard water though. it might take care of the problem, it might take a mix of bypass, and softened water.....
Like my irrigation water is on well, this is so full of iron, it's ok I guess for grass, it kills fruiting plants though, and even my grass is mostly weeds or centipede grass. Stains my house a nice shade or red/brown where the sprinklers hit that I have to clean off every month also. My city water is fine, that irrigation water from the well I can't even use it in my pool because of the staining it will cause to the surfaces. I'd never dream of putting that in an aquarium.

I have always had to use softened water because our well water is like SparkyJones’ - everything is touches turns orange if it’s not softened. I tried using seep hoses in my garden once, but the rust in my water plugged them after one use.