Topping off in hard water tanks

[JettsPapa]

Hello,

My tanks run about 8.2 pH, with GH and KH both high (close to 300 ppm using AC test strips).  For the first two years I kept fish I topped off with tap water, but decided I should probably be using RO or distilled water instead, although I hadn't detected any problems in the tank.  I've been doing that for a month or so without any noticeable improvement, and in fact I don't think the plants are doing as well in several of the tanks.

Also, while it's not a big expense, buying 6 - 8 gallons of water per week adds up.  (That's spread out over 9 tanks, ranging in size from 5.5 to 40 gallons.)

Does anyone have any hard data on whether or not topping off with hard water is a problem?

[KaitieG]

I don't have any data, though I'll be watching to see what others have.  I have similar water to you, though, and I top off with tap water.  I tried it with distilled water for a while, but it just got to be a hassle, and I haven't seen any detrimental effects so far (3ish years) with tap water top offs.

[Fonske]

I have ~7.6-7.8 pH, ~12 dGH and ~9dKH in tap; my tanks are small and evaporation is ~1/2" per day. After topping off with tap water for a while, dGH went to >15, and dKH to ~ 12.  Didn't see any effects on the fishes I kept at the time (guppies, danios, bitterlings) or plants, neither negative nor positive. These days I top off with RO only softies like bettas, others seems fine with the tap (and large water changes every week).

[PineSong]

Hmm, this is interesting to me. What would the dangers (theoretically) of the tap water top offs be--accumulation of minerals? I have hard water and have only ever topped off with Primed tap water. But... I do use spring water for my bettas because I noticed when I moved here that I had short lifespans compared to where I used to live, and attributed that to the hard water here. 

[Mychala]

@PineSong @Fonskedid you notice they are more lethargic and generally don't eat as well? My tap ph is 8.2 hard as a rock and I typicIlly use fluval stratum to keep it down. My stratum recently must have ran its course and my ph is back up. The betta isnt sick but just doesn't act the same... I'm thinking I'm putting new stratum in to see if it fixes the problem

@JettsPapa for several years I have kept about a cup of fluval stratum in my clean water bucket and age it overnight. It drops my ph from 8.2 to 7. It's cheaper than the distilled water over time. Just make sure the ph is stable before you change water and leave the stratum in the bucket.

Edited February 2, 2022 by Mychala

[Fonske]

On 2/2/2022 at 9:33 PM, Mychala said:

did you notice they are more lethargic and generally don't eat as well?

No, I didn't see these symptoms, my bettas have always been gluttons and quite active. Their issues always started as problems with fins or skin in general. After changing to softer/lower pH/filtered water (among other things), they seem to be doing much better.

I use only gravel and sand, so no experience with pH variation due to active substrates.

[Guppysnail]

I have 7.6 liquid rock. I’m not a top offer I’m a changer though. My plants deplete minerals even changing and it gets softer in my tank. I can’t see any harm in topping off a planted tank to replace lost minerals unless you have substrate that intentionally lowers ph. my neo shrimp colonies in all my tanks thrive. If it is unplanted over time it may build up I would think. 

[Levi_Aquatics]

I know in saltwater aquariums they top off with fresh water to keep the salinity stable because the minerals don’t evaporate with the water. I’m not sure however if this translates to freshwater. 

[Andy's Fish Den]

On 2/2/2022 at 9:41 AM, Levi_Aquatics said:

I know in saltwater aquariums they top off with fresh water to keep the salinity stable because the minerals don’t evaporate with the water. I’m not sure however if this translates to freshwater. 

The salt and minerals don't evaporate in salt or freshwater.  I have an RO unit because of keeping reef tanks in the past so I always have some on hand, and do top offs with the RO water to try to keep the parameters stable. I am not sure how much it helps, but in my mind it does LOL.

[JettsPapa]

On 2/2/2022 at 8:25 AM, Guppysnail said:

I have 7.6 liquid rock. I’m not a top offer I’m a changer though. My plants deplete minerals even changing and it gets softer in my tank. I can’t see any harm in topping off a planted tank to replace lost minerals unless you have substrate that intentionally lowers ph. my neo shrimp colonies in all my tanks thrive. If it is unplanted over time it may build up I would think. 

My initial thinking was that the minerals might build up too much, since they don't evaporate out, but you may have a point.  Maybe the plants need the minerals.

[PineSong]

On 2/2/2022 at 8:33 AM, Mychala said:

@PineSong @Fonskedid you notice they are more lethargic and generally don't eat as well? My tap ph is 8.2 hard as a rock and I typicIlly use fluval stratum to keep it down. My stratum recently must have ran its course and my ph is back up. The betta isnt sick but just doesn't act the same... I'm thinking I'm putting new stratum in to see if it fixes the problem

 

I'm no water chemist, unfortunately, so I don't understand all the ins and outs, but my tank water tends to be low in pH--6.8 to 7 with low KH as well as very hard. 

My bettas have always eaten well, but I've had some slow down and down and down until they die, and others just "up and die" without noticeable symptoms. That said, Over the course of the past several years there have been many periods when I was working a million hours and not home to observe as much as I have been the past two, so I may well have missed things then that I would not miss now.