Need help with pH issue

[06redragtop]

We have a 72 gal Discus tank. The city water here is 6.8. However since we set up the tank 6 month ago. The pH in the tank has risen to 7.4. Not good for Discus and over the last couple of month lost several and i beleive its due to the pH. Ammonion, nitrite and nitrate are all good. I do 30% water change and vacuum once a week and 50% once a month. Grave substrate. Java moss and java fern for plants. Lava and river rocks for decorations. Have just added drift wood to see if that will help.
I do not understand why the pH has increased and until i get it under control we are not going to add anymore Discus.
Any suggestions

[Iminit]

I would say you need to be changing more water. I’d start with 50% twice a week. How old are the discus and how big? 7.4 is fine for discus by the way. But since your tap is 6.8 it’s best to keep the tank close to the tap. Next you could get a barrel and age your water before putting it in the tank. To test just fill a 5g bucket and test ph. Let sit for 48hrs and see what the ph is than.

[06redragtop]

Thx for the response.
If my water quality is fine why up the water changes?
I guess my biggest question is why is the pH loosing its acidicy

[dspeers]

That is a puzzle, usually biological processes in an aquarium decrease the pH.
Test 1, age and aerate tap water in a 5 gallon bucket with aeration, if pH rises then it is due to excessive dissolved CO2 directly from the tap.
Test 2, measure gH and kH immediately after water change and then immediately prior to next, if both go up then something in your tank is dissolving and affecting your pH, usually due to limestone.
What does nitrate level good mean to you?
The increase water change recommendation is a general one based on your having lost several discus ( I am reading Tom's mind, he may have additional observations). The pH of 7.4 is not the issue although the bounce from 6.8 to 7.4 weekly probably contributed as a stressor. For now I would probably change 30 % every other day or even 20% daily to minimize pH bounce until I had a handle on what was causing the paradoxical pH rise. You really need to age some water immediately to see if that is the issue and if so then add aging to your regimen with every water change. If that is in fact the case then I would go with the 50 % (aged) twice weekly that Tom suggested because the pH measured immediately from the tap is factitious, true pH is the value after the dissolved CO2 has normalized.

[06redragtop]

Thx for the indepth answer. I've just learned how kH can affect my water quality but isn't gH for salt? I had picked gH / kH test kit today as i read high kH could prevent changing the pH. I ve added driftwood and picked up some aquarium peat. Is it possible there is limestone in lava rock? I had checked other rocks before using them. Ill be disappoint if thats the case. They add a nice effect. This is a community tank. Electric Blue Rams are also suffering

[dspeers]

gH is a measure of divalent cations, Ca++ and Mg++. If your pH is rising due to limestone aka calcium carbonate then your gH will rise with your kH. kH measures carbonate and bicarb concentration. If there is something in the rock that would raise your kH without increasing gH someone with more knowledge needs to comment, would be like adding Sodium bicarb aka baking soda but I don't know what in the tank could act like that. Lava rock should be inert.

The reason high kH resists pH change with the addition of an acid is because the carbonate or bicarb combines with the H+ cation producing CO2 and H2O so the kH will drop before the pH, that is the concept of buffering. If there is something dissolving into the water another clue will be a rapid rise in TDS/EC relative to your tap water. Home TDS meters do not actually measure TDS, rather they measure electrical conductivity (from which a TDS value is estimated) which correlates to dissolved salts of all varieties.

Before you try to address all the above, you need to rule out excessive CO2 in your tap water, have you tried aging your water? Also one other thing I forgot, you need to heat the water while aging. Assuming your tank is warmer than your tap your dissolved CO2 (or any dissolved gas) is inversely related to the temperature of the water, as temp rises, CO2 drops & pH rises. Point is though that water does not in general show a rise in pH only from aging. Avoiding this transient pH shift is one of the major reasons folks age water prior to doing water changes. A stable pH of 7.4 is not a problem.

[06redragtop]

Ill have to get some gear together to age some water. My tank is running between 82 and 83 deg. Depending on which thermometer im using. I try to keep the water from the tap +/- 1 deg when adding. Both kH and gH are 5 drops. I was only able to get a fulval test kit. Im now wondering if the liquid plant fertlizer has contaninated the tank

[kev1310]

Your PH could be rising for a few reasons, one of the rocks could be adding carbonate hardness, or quite possibly although your PH from the tap is 6.8 it is higher than this naturally once aged and any dissolved gases have escaped. Your PH is unlikely to have caused you to lose discus though unless they're wilds, I'm breeding domestics at 7.8. I doubt the swing is causing any issues either, I've measured a swing of 0.5 PH in planted tanks between night and day due to photosynthesis alone.

The gravel substrate and a build up of organics in it would be a possible issue though unless you thoroughly vacuum it regularly.

[kev1310]

Oh and I mean not just vacuuming over the top of the gravel but removing any debris contained within it.

[captainandy]

The pH of 7.4 or even the swing, may not be what is killing your fish.
What type of pH monitor do you use. Let your tap water sit for a day and then measure the pH,

You should bring in a sample of tank and faucet water to your LFS and have your parameters checked professionally

[Oxboy]

82 degrees is too low for amateur keepers like a lot of us. A constant 86 is better.

[06redragtop]

I want to thank everyone for your tip and advice. Its all been very helpful. I need to get more info on where my supply of fish are coming from. I need to find out more about my water. I need to be more thorough in vacuuming. I guess ticking the grave is not doing anything. I beleive the rocks are ok. I did test them with muriatic acid. No foaming. Im also thinking i may have over fertalized when my plants were doing pourly. And l can stop freaking out about th pH. Again thx to everone it not hopeless after all. I just got to do a little more work.

[Oxboy]

The gunk down in the gravel is the silent killer for discus, particularly young ones. I've seen posts on the web of people with gravel doing a deep vacuum with each WC several times a week and the brown silty particles still come up every time. I suppose you could go heavily planted and feed less to minimize the gunk but then you encourage other problems like difficulty vacuuming, overfertilizing and fish underfeeding/underdevelopment.

The best BEST advice when starting out with discus is bare essentials only...keep it simple....minimize all the moving parts until you get the hang of it. IOW: Bare bottom. No plants. Steady 86 degrees. 4+" discus only (no other species) in group of 6 or more. Several WCs and tank cleanings a week. No beefheart, but a variety of quality flakes, FD and granules. With this recipe, you will the fish to thrive. Then and only then do you introduce other variables (like plants, ditherfish, rockscapes etc) if you're feeling daring.