Lighting question. Please help!!

[jarsofkimchee]

I just swapped my old flickering t8 fixture with a new 320watt t5HO fixture on my 100 gallon planted tank. After a water change today I noticed that 2 of my discus started breathing at a more rapid rate, so I checked my water parameters and my pH read 6.8! Before switching to this t5HO fixture, my pH was kept at a constant 7.6! I am guessing this decrease in pH is due to the high output t5's. I do not run CO2 in this tank. What should I do? Any advice? I am a newb to planted tanks/high output lighting. Also, will this decrease in pH swing back up tomorrow after the dark/night photoperiod? Thank you for your help!

[pcsb23]

I would suspect the change water and not the lights.

More light means the plants could grow faster provided there are no other limiting factors. Faster growth consumes CO2 from the water so if anything the pH will rise and not fall, this is why we add CO2 in high light tanks, as it very quickly becomes the limiting factor - i.e. it gets used faster than it can dissolve from the atmosphere.

Basically during the day plants use CO2 and produce oxygen, during the night they use oxygen and produce CO2 so over night, if anything the pH will fall.

[jarsofkimchee]

Thanks for your help Paul. That makes a lot of sense. I've been keeping this tank for about 3 months now, and the only thing I've changed since the initial set up were the lights from NO to HO. Hmmm... I wonder what the cause of this mysterious pH decrease is then.. I use straight tap water with Seachem Safe only. No Discus or Acid buffers or anything like that. My tap water comes out with a pH of 7.6 and does not change when aged for 48 hours. Anyone have any ideas of why my pH dropped? I am completely bewildered at this point

[pcsb23]

It could be as simple as the bio filter taking hold. The simplistic process is ammonia --> nitrite --> --> nitrate but one of the by products at the end of the cycle is nitric acid

[pcsb23]

I should have added, do you know what your kh is? or the tds??

[jarsofkimchee]

I should have added, do you know what your kh is? or the tds??

Thanks for your help! My water parameters are ph 6.8, ammonia 0, nitrite 0, nitrate 20, kh 80. I do not know what the tds is atm. Could double dosing with seachem safe at 86f be the cause? I know the bottle says not to double dose at that temp but another source told me it was fine, especially if the tap water is high in chloramine. I am still stumped and very worried for my fish. Thanks again for all of your help!

[pcsb23]

Thanks for your help! My water parameters are ph 6.8, ammonia 0, nitrite 0, nitrate 20, kh 80. I do not know what the tds is atm. Could double dosing with seachem safe at 86f be the cause? I know the bottle says not to double dose at that temp but another source told me it was fine, especially if the tap water is high in chloramine. I am still stumped and very worried for my fish. Thanks again for all of your help!I'm assuming the kh is in ppm, which means it is fairly soft water. Given that it is soft then pH can change easily, so I would put the change down to the bio filter. The higher light may stress the discus for a while until they adapt, the pH change is not significant so that is unlikely to affect them.

[jarsofkimchee]

I'm assuming the kh is in ppm, which means it is fairly soft water. Given that it is soft then pH can change easily, so I would put the change down to the bio filter. The higher light may stress the discus for a while until they adapt, the pH change is not significant so that is unlikely to affect them.

Yes that's 80ppm. Sorry I didn't add that. Thanks for all your help Paul. I have never run into this problem before as I have 3 other tanks that stay at a stable 7.6. Should I give all bio filters and sponges a good squeeze each?

[pcsb23]

Yes that's 80ppm. Sorry I didn't add that. Thanks for all your help Paul. I have never run into this problem before as I have 3 other tanks that stay at a stable 7.6. Should I give all bio filters and sponges a good squeeze each?I give sponges a squeeze once a week, use tank water or dechlorinated tap water. If you run cannisters, just rinse the media once every couple fo months, again use tank water or dechlorinated tap. I fit pre filter sponges on the intakes to cannisters, keeps them cleaner for longer!

[jarsofkimchee]

I give sponges a squeeze once a week, use tank water or dechlorinated tap water. If you run cannisters, just rinse the media once every couple fo months, again use tank water or dechlorinated tap. I fit pre filter sponges on the intakes to cannisters, keeps them cleaner for longer!.

Ok will do! Thanks again for all your help. I learned a lot this afternoon