Pearling in the morning but not in the evening?

My tank has the odd pattern of strong pearling within minutes of the lights coming on in the morning, but the pearling slows down to almost nothing by evening. What could be causing this?

Tank stats:

180 gallon
495w pc lighting
EI Dosing
CO2 injection during the day (PH 7.8 drop to 6.2), air injection at night
gravel thorughly cleaned one month ago
medium fish load

 

Re: Pearling in the morning but not in the evening?

I'm sure about the CO2. I have a PH controller bringing the PH down to 6.2 during the day. The CO2 turns off when the lights turn off at night. The PH is around 6.6 in the morning before the CO2 turns back on.

The one thing I've noticed is that if I leave the air pump on during the day together with the CO2, I get better pearling in the evening. I know that pearling increases oxygen saturation, but can oxygen saturation have an affect on pearling?

 

Re: Pearling in the morning but not in the evening?

I dose standard amounts each morning. I do two 30% water changes per week.

My solenoid is working properly. The CO2 is off at night, but the PH only rises from 6.2 to 6.6 (degassed water is PH 7.8)

The idea of O2 dissolving into the water before we can see it is a concept I never understood. During strong pearling, there are steady streams of bubbles coming from the plants. I can't imagine that in low O2 situations, these streams of O2 are dissolving so quickly that we just can't see them.

Or do plants also produce O2 that is not visible and pearling is just the excess? Can anyone clarify this?

 

Re: Pearling in the morning but not in the evening?

In response to my own post:

If I assume that visible pearling only occurs when the water is saturated with O2 (which I still don't understand the reason for), then the most likely explanation for this "reverse pearling" pattern is that there is something decomposing in my tank that is absorbing all the oxygen.

I thoroughly vacuumed my gravel last month, so it can't be that.

I clean my filter once a week so it can't be that.

My only guess would be a large piece of driftwood that I added to the tank 3 months ago. The base of the wood has white fungus growing on it which I'm assuming means that the wood is decomposing in those areas. Could this be causing it?

 

Re: Pearling in the morning but not in the evening?

Wouldn't my PH go up as the CO2 is used up? My controller keeps the PH steady at around 6.2.

I'm injecting CO2 into the system just before my pump, then back into the tank on 2 opposite sides through the pump outputs.The PH drops very quickly when the CO2 comes on in the morning and stays low all day. I recently tried to lower the PH to 6.0 but some of the fish were showing signs of distress so I raised it back up.

I'm also dosing excel every morning to supplement the CO2 in case that was the problem, but it doesn't seem to have an effect.

Overall, since I started EI dosing 3 weeks ago, there is a dramatic improvement in the health of my plants, but coming home to a tank with no air bubbles in it at the end of the day keeps giving me the feeling that something just isn't right.

 

Re: Pearling in the morning but not in the evening?

I'm maxed out on CO2. I would add more, but the last time I checked, having dozens of dead fish floating around the tank may lead to an algae outbreak.

Seriously though, if my tank stays exactly as is, I am very happy with it. With EI dosing, I can finally grow any plant I want. Even my HC is thriving - I was never able to grow it at all before. I just wonder if the lack of pearling is a sign of bad things to come.