PH Mysteries

[DiscusMark]

I have a thriving 55 gallon tank with six juvenile Stendker discus (4.5", healthy, and growing very rapidly). The tank has a pool filter sand substrate, some plants in pots (so that I can clean more easily), and more than adequate filtration (fluval 406 + hydro sponge).

My question is about PH swings during water changes. My practice so far has been to change 50% of the water every other day. My tapwater has a PH of 9, whereas the tank has been steadily at 7.5-7.6. I pump the tap water into a 32 gallon barrel, where, after aging for 24 hours, the PH has been dropping from the 9 down to 7.8, at which time I treat it with Prime and put it into the tank.

Over the past few months, however, the PH hasn't dropped as much with agitation, and the PH out of the tap has crept up to 9.2. Now I can only get it to drop to about 8.5 with agitation.

I tried a smaller (30%) water change with the 8.5 PH water the other day, and the fish seemed as happy as normal. (One has even laid eggs in recent weeks, though I have no plans to breed the fish.) The PH in the tank quite quickly stabilizes after water changes at around 7.6-7.7.

Is this swing during water changes (briefly up, then back to normal) a problem, or should it be OK? Other related thoughts?

[pitdogg2]

I would do my normal percentage of water changes. In nature they're swings and like your tank they will acclimate PROVIDED there is not a crash in ph or spike in ph. I think what you're seeing is the normal ph swing in your local area. As long as there have not been lots of rain where they are adjusting for that or a water main break where they just dump in all kinds of chlorine and ammonia.

[Clawhammer]

In my area, the pH and KH go up a little in the summer. The reason for this is because winter is wet season and 100% of the water is drawn directly from a natural reservoir, however, the summers are dry and they often need to supplement the natural reservoir with water contained in manmade concrete reservoirs. The acidic water pull alkalinity out of the lime in the concrete, increasing pH and KH. The absorbed alkalinity is not diffused by aeration.

Another possibility is that your municipality is playing with the water chemistry. Many municipalities are dramatically increasing the pH of the water in order to prevent lead pipe corrosion / lead contamination and it is pretty apparent that is being done by your water company based on your pH before and after aging.

Anyway, if the fish are acting normally during the revised water change procedure, I wouldn't worry too much. The pH scale is logarithmic, so the 30% WC with 8.5 water is not changing the pH a lot. Also, discus are more comfortable with a slight upswing than downswing.

Are you doing the 30% daily? Every other day would be not quite enough for growing juvies IMO.

[ssevasta]

I totally agree with claw hammer and I also suggest that you increase your water changes to at least 50% per day or 75% every other day. By increasing your water changes and feeding 4-5 times daily you will ensure that you get the optimal growth rate for your fish. I also have a relatively high ph and hard water but I've had great success by following the schedule I recommended. Good luck

[DiscusMark]

Thanks all--much appreciated. I've been doing about 60% every other day, but had reduced it to 30% because of the PH concern. I tried another 60% change yesterday, though, and all the fish are acting well.

[ssevasta]

Clean consistent water changes can never hurt your fish :-)

[Dragondiscus]

Hi there , I am new to the forum and this might be an old tread. but I have a 55 gallon with 6 discus of different types, I got them as juveniles, I only do weekly water changes that was fine until I started having problems with one of my discus one of the larger ones in the tank, started loosing size and have white worm like discharge, the other discus are fine to date, but cannot seem to get this discus to overcome this infection. it is active not hiding fins not clamped but not eating that I can see, so started doing water changes every three days. have been discharging that white substance a lot more now, but still not eating. don't know what to do next. I went with a bear bottom tank sponge filter side filter and driftwood to help keep the water soft, but it is always at 7.2 PH , 0 ammonia.

[Clawhammer]

Hi there , I am new to the forum and this might be an old tread. but I have a 55 gallon with 6 discus of different types, I got them as juveniles, I only do weekly water changes that was fine until I started having problems with one of my discus one of the larger ones in the tank, started loosing size and have white worm like discharge, the other discus are fine to date, but cannot seem to get this discus to overcome this infection. it is active not hiding fins not clamped but not eating that I can see, so started doing water changes every three days. have been discharging that white substance a lot more now, but still not eating. don't know what to do next. I went with a bear bottom tank sponge filter side filter and driftwood to help keep the water soft, but it is always at 7.2 PH , 0 ammonia.

It sounds like your fish may have HEX, but not enough information was provided to confirm. Your best bet is to create your own thread in the "Emergency" section and make sure to fill out the questionnaire on your tank setup. Also, including pictures of your tank and sick fish is helpful. Good luck.