Dwarf Hairgrass Browning in Cycling Tank

[linkandnavi]

Hi all,

Hoping for some advice. My 120 (US) gallon (450 litres) planted tank is nearing the end of its cycle. The plants went in four days ago. There is a layer of Tetra Complete (plant) substrate, covered by a layer of 1mm fine black gravel. There are root tabs evenly distributed throughout and the tank is co2 injected to approximately 30ppm.

Lights are currently running for six hours a day (10am to 4pm) although it will be getting some sunlight too. Co2 is running for five hours a day (9am to 2pm). The intention is to up those hours in two or three weeks when the plants are more established. I'm fertilising with Seachem Flourish every 3-4 days.

Everything seems broadly fine except that some of the dwarf hairgrass (I'm aiming for a carpet) seems to have browning leaves. The hairgrass is Tropica`s "1-2-Grow". I`ve included some pictures of what I mean. There is algae in the tank at the moment - some of which is visible in the forefront of the pictures. I`m not too worried about that, given a bit of an imbalance in the tank is expected while it is cycling and there will be some algae eaters in there once the cycle is finished. I've read some conflicting information online about browning dwarf hairgrass. Should I be increasing the light and co2? I accept that may increase the algae problem but I'm ok with that if it solves the problem as the algae will be temporary.

I've also seen it suggested that I should trim the dwarf hairgrass about now to make it carpet quicker. Any thoughts? It doesn't seem there is too much to trim at this point.

Thanks.

g

 

[GPaul]

I am sure it will bounce back , same thing happening to my tank , they are in transition phase.

 

[Zeus.]

Lights are currently running for six hours a day (10am to 4pm) although it will be getting some sunlight too. Co2 is running for five hours a day (9am to 2pm)

My 120 (US) gallon (450 litres)

One hour to get 450litres to a stable [CO2] is pushing it unless you have twin solenoids on your CO2 regulator, have you done a pH profile?

I've also seen it suggested that I should trim the dwarf hairgrass about now to make it carpet quicker. Any thoughts?

I would wait for some time yet. Two pics below are 5 weeks apart with a DSM




The new root growth is a clear sign that the plant is thriving, trimming a carpet too soon will leave it with less leaves to catch the light/energy it needs for the transition phase and then to grow

 

[linkandnavi]

I am sure it will bounce back , same thing happening to my tank , they are in transition phase.

Thank you. I'll stick with it! Always a habit of thinking things are going badly, when it usually just means sticking with it

 

[linkandnavi]

One hour to get 450litres to a stable [CO2] is pushing it unless you have twin solenoids on your CO2 regulator, have you done a pH profile?



I would wait for some time yet. Two pics below are 5 weeks apart with a DSM
View attachment 164574

View attachment 164575

The new root growth is a clear sign that the plant is thriving, trimming a carpet too soon will leave it with less leaves to catch the light/energy it needs for the transition phase and then to grow

Thank you. I can see some routes pushing down at the front of the tank so yes, a good sign. I'll stick with it!

I'm not sure what you mean by 1 hour for stable co2 sorry? Co2 is currently running for 5 hours a day and I'll up that and the lighting once the plants are more established. pH was 8 prior to co2 injection starting (that's my tap water and the level in my non-co2 tank). Since I began co2 injection it now sits steady at 7 (confirmed with pH test kits, not just drop checker).

Thanks again

 

[Zeus.]

To check for CO2 stability you need to take pH pre CO2 on then every 30mins till CO2 off and at lights on, make a graph and see if it peaks at lights on and if it remains stable from lights on till CO2 off



Without a pH profile or years of experience getting a stable pH is hard. @ceg4048 covers the reasons for stable CO2 better than myself, in short stable means no pH change relatively from lights on till CO2 off. Getting a pH profile like above isn't possible, but was can get close

What I mean is that if you are struggling with CO2 stability, or are having difficulty keeping high concentrations, then it's best to focus efforts on the first half of the photoperiod and not worry so much about the second half. If you are running very strong lighting then you are really pushing the plants and it's necessary to have the CO2 going. After 4 hours, if you turn the gas off, the water stays saturated for a couple of hours after the valve closes and the concentration trails off. So if you have an 8 hour photoperiod and you turn the gas on 2 hours before lights on, you can turn the gas off after 6 hours. So the gas is still running for 8 hours but it's on-off cycle is offset by the amount of time you turn it on prior to lights on.

We have a fairly well grounded, basic understanding of the photosynthetic processes.
A. We understand that Rubisco's job is to capture CO2 molecules and to deliver the molecules to the Calvin Cycle reaction centers. We know that Rubisco is hugely expensive and consumes a lot of resources to produce and to maintain. In low tech tanks, where the CO2 concentration is low there is a much higher density of Rubisco in the leaf because you need more of the protein to capture the small amounts of CO2. In gas injected tanks, the Rubisco density in the leaf is lower.

B. We also know that during Calvin Cycle, the fixing of Carbon involves some intermediate carbohydrate products until the final product is a type of glucose.

So, for item A. we know that when the plant senses that high concentrations of CO2 is available, it responds by reducing the production of expensive Rubisco. When it senses a lower CO2 concentration it must increase Rubisco production, however because this protein is so complicated and heavy, the increased production requires 2-3 weeks in order to change the density in the leaf to match the new gas concentration level. So it is much easier to reduce production than it is to increase production. When increasing gas injection therefore, it hardly takes any time to see an improvement in health. When lowering the concentration, the plant will suffer because it must now ramp up Rubisco production to account for the loss of CO2 availability.

When increasing the light, the plant must reallocate resources from Rubisco production/maintenance in order to deal with the increased radiation. This may entail new pigment production for protection. When the light is reduced, the plant then reallocates the light gathering proteins and can devote them to Rubisco production/maintenance.

So when we mess around with light and gas, we have some degree of predictability.

 

[foxfish]

It is always difficult to quote figures due to the many differences from one tank to another but as a guide you can expect it take around 2-3 hours from the C02 being turned on before the tank water is up to 30ppm.
With big tanks it can take longer still!
So as Zeus points out a PH graph is a really important aid to help you get it right.