Sudden drastic drop in pH???

[Fishmutt]

I've been cycling a 90g tank for 4 months now. Never really got it to work, ammonia would drop and I'd not see nitrite. Then nitrite would appear and ammonia would suddenly stop dropping. Then both would stop. Frustrating

A friend recommended raising my tank temp to 86 from 78 to help speed up bacteria reproduction. I did and nitrite fell to 0, but ammonia stayed stuck at 2.

Then I did a weekly pH test, normally it's at 7.6-7.7. The test read somewhere in th 5s!! I dropped back to 78 degrees and did two 50% water changes about 12 hours apart. Each time I measured pH at about 7.6 right after the change, in the low 6s/high 5s 12 hours later.

I have no fish in this tank and about 20 plants. I have been using Flourish and Flourish Excel, but I've been careful not to OD on the stuff.

I read that low pH will convert ammonia to ammonium, so that may explain why it stuck. But what could torpedo my pH like that? Warming the tank? Any ideas?

Had no idea this hobby would be so frustrating.

 

[bud29]

A pH crash can happen during a cycle and stall it. That is never a good thing.

 

[Andy8114]

I've been cycling a 90g tank for 4 months now. Never really got it to work, ammonia would drop and I'd not see nitrite. Then nitrite would appear and ammonia would suddenly stop dropping. Then both would stop. Frustrating

A friend recommended raising my tank temp to 86 from 78 to help speed up bacteria reproduction. I did and nitrite fell to 0, but ammonia stayed stuck at 2.

Then I did a weekly pH test, normally it's at 7.6-7.7. The test read somewhere in th 5s!! I dropped back to 78 degrees and did two 50% water changes about 12 hours apart. Each time I measured pH at about 7.6 right after the change, in the low 6s/high 5s 12 hours later.

I have no fish in this tank and about 20 plants. I have been using Flourish and Flourish Excel, but I've been careful not to OD on the stuff.

I read that low pH will convert ammonia to ammonium, so that may explain why it stuck. But what could torpedo my pH like that? Warming the tank? Any ideas?

Had no idea this hobby would be so frustrating.

Are you using co2 ? when you say 20 plants you mean live plants right ? And could you tell me what florish is ? im guessing a bacteria supplement

 

[ThomasG07]

I recently put just 1 live plant in my cycling tank as well and 2 days later the PH plummeted and the cycle stalled. I yanked that sucker out of there so fast.

 

[jetajockey]

The plant isn't the problem, it sounds more like a lack of buffers. This kind of ph crash is somewhat common when fishless cycling.

 

[Fishmutt]

Are you using co2 ? when you say 20 plants you mean live plants right ? And could you tell me what florish is ? im guessing a bacteria supplement

Thanks for the responses everyone. Yes they are live plants but I am not injecting any CO2. I know CO2 lowers pH, but if anything the plants should be absorbing any CO2 and raising my pH, not lowering it. Flourish is a plant fertilizer, been using it a month and my plants look great. Don't think it's what caused the sudden drop.

I've heard that live plants shouldn't affect a cycle but I could be wrong. The only other living things in the tank are an infestation of pouch snails that came with the plants.

The only change I made that corresponds with the pH drop was raising the temp from 78 to 86.

Thanks for the help all, I'll just try starting from scratch and buying pH chemicals I guess.

 

[Fishmutt]

The plant isn't the problem, it sounds more like a lack of buffers. This kind of ph crash is somewhat common when fishless cycling.

I've heard of buffering but I don't really understand it that well. Something about how quickly minerals are absorbed or something like that. I'll read up on it and see if that's the culprit.

Thank you jeta.

 

[jlk]

I agree with Jeta- it sounds like your water does not have sufficient buffers. As your bacteria digest the ammonia, they use the available buffers (carbonates) to process ammonia. Buffers keep your your ph stable- when they are gone, your ph crashes. The plants & ferts are not affecting your cycle. Increasing the temp helps to grow your bacteria colonies faster (multiply quicker) and process ammonia at a faster rate which equates to your buffers being used up faster as well.

No ph chemicals are necessary. If your ph is low right now, do a large water change (50-75%) with temperature matched, properly conditioned water. Then add a mesh bag/piece of pantyhose of crushed coral, argonite, crushed seashells or cr limestone to your filter- this will help to increase your buffer (carbonate or KH) levels. You will need to monitor your ph daily & adjust the amount you have until your tank stays stable at its normal ph level. This may mean adding some more buffer if ph drops or removing some if it jumps too high. Hope this helps!

 

[aqua_chem]

Do you have any idea how hard your water is? Any buildup around faucets, etc?

 

[Fishmutt]

Starting to love this forum!

I researched buffering and it sounds like it is exactly the problem. My tap water is very, very soft (GH=3) which apparently means it lacks buffering agents. I am going to get some crushed seashells and put them in pantyhose in my wet/dry sump. That's safe for freshwater, right?

I did not know that bacteria uses up some of the buffering agents which explains why the temp change indirectly led to the sudden drop and why things were going good for awhile then suddenly stalled. Life makes sense again!!

Thanks everyone, especially jeta, jlk and aqua_chem.

 

[aqua_chem]

The buffering content is your KH. GH is just the mineral content. The two together make "hard water".

 

[Fishmutt]

The buffering content is your KH. GH is just the mineral content. The two together make "hard water".

Ah makes sense. My water is soft so it lacks both. All I really need to increase is the carbonate hardness (KH) I think.

Thanks again all.

 

[jetajockey]

You'll want to raise your GH also, it's what keeps the KH stable. Crushed coral or aragonite work well, for a more immediate effect you could dose calcium/magnesium or dolomite Camg(co3)2. The former method mentioned is more of a long term solution, the latter requires periodic redosing.