Freshwater Chemistry help needed!

I have a 240l planted tank which has been running for almost 3 years. I confess I have not been taking water chemistry readings for the last year until recent fish losses. I have just bought a master test kit and the readings were : Ammonia - 0, Nitrate - 0, Nitrite -0 (all as expected in a well matured heavily planted tank). The pH however has got up to 8.2, I am certain that this is the cause of death of the fish and am taking steps to correct it. What I don't understand is how this has happened.
I do regular water changes with 50:50 R.O and tap water. Our tap water is pH 7.5. There are 4 large pieces of bog wood in the tank and no rocks. The gravel is lime free. To back this up I tested the kH and it is less than 2. Why has the pH gone up? and what should I do to bring it down slowly to between 6.5 and 7.0 - I think buffers may fix soluble nutrients and make them unavailable to the plants?
Any help would be much appreciated.

 

wow, that is a problem. Are you running south american fish in the tank, asking because the low PH you want. Im also kinda stumped on your problem. What is wired though is your nitrate reading is really low. How dense is your tank planted?? In most freshwater tanks that Ive had, nitrates have always been around 5-10ppm. It is just how the freshwater tanks runs for me. Are you doing large water changes ever day?? Buffers will only stablize your ph, and can also raise it. I would do small water changes with only tap water for a few days. You said you tap was 7.5, so that will bring your ph slowly back to 7.5, then start your normal tap/RO water to stablize it back to were you want it. Just make sure you dont do more than a 5% water change, and do more than .5 Ph change a day, or you will loose more fish. It is way harder on fish to go from a high ph down to a low ph, then from low to high. Good luck,

Michael

 

Limestone was my first guess but you mentioned you don't have any. hmmm.. this is interesting. Any more info? I'll do some digging...

 

Thanks Michael,
Yes it is a S. American tank, tetras and Rams. It is very heavily planted and my best guess is that the plants have lowered the CO2 levels to almost nothing and that this has caused the increase in pH. I have started adding CO2 again (I had stopped a year ago because the plants seemed to be doing fine without). This is bringing the pH down well, but maybe too quickly. I've added more tap water to incraese the kH which should increase buffering capacity. I've just got to hope the change isn't too sudden.
Ben.

 

Good to hear, I never thought about the co2, lol. That will bring the ph down around .5 to 1 point in PH. Hope you dont loose anymore fish, I know how hard it is to keep those little rams alive anyway.

Michael

 

I stopped adding co2 for the same reason with my planted tank. I didn't give any thought to pH at the time. I am very curious now. I just have a tiger barb in there that is going on 8 years old if you can believe it. He seems fine as usual but I think I will still test. Thanks for the info.

Upload some pics of your tank. I'd love to see it.

 

Co2

Of course the amount of co2 needed to be injected into the tank all depends on how densly planted the tank is, lighting, and the level of the other micro and macro nutrients. My tank personally grows a lot slower when the co2 level gets low, which isnt always a bad thing (less pruning!).
I hope your tank is doing better 8.2 is pretty high for those rams. As I am sure you know with a kh of only 2, too much co2 will cause a large ph swing.

Good Luck
Travis

 

Awesome tank Travis! 8)
What size is that? Ahhh.. 55. Very nice.

 

thanks Matt

Thanks Matt, I have been keeping freshwater tanks for many years and have just recently gotten into reef tanks. I personally believe a nice densly planted freshwater can rival a nice reef aquarium;D

Travis

 

WOW, I really like you tank. Ive only got one FW left. I had two 55's but one had to go for the new 100 gallon salt, so bye bye rift valley . But oh well, salt is filled with a whole new world of challenges. Lol, im gonna take this as an invatiation to post mine, he he. But I like yours alot more. Ive just got two discus, and 3 angels, but there going strong. Good luck, and let us know what happens with your tanks,

Michael