How to "Balance" a High Tech Tank

[Merlin647]

I decided I wanted to use a 20g high to setup a high tech tank a couple months ago. All my tanks have been planted, but not aquascaped or co2 injected or anything. My main issue is algae control, at first I just had bright green algae on the glass but now I'm dealing with algae on plants and rocks too. Mainly I've got dark green spot algae on my ludwigia leaves and a bit of hairish algae on my hairgrass. It's gotten to the point that I have to clean all the walls of the tank thoroughly every week or it turns into a green murky mess when I look at it.

Here's what I have going on: my light is a Finnex Planted+ 24/7 CRV (was on max for ~8hrs/day now on the 24hr cycle), Seachem ferts(I'll attach a link to my schedule), co2 running about 1 bubble/second, and a Fluval 207 Filter on about half power. I've got a couple honey gourami, 5 ottos, and 4 amano shrimp. My NH3 is 0ppm NO2- is 0ppm and NO3- sits around 10-20. I used inert substrate and I've used flourish tabs rather densely in the substrate. I use RO water and do a 25% water change each week.

I've tried to fix the problem myself, but after reducing lighting to around 4hrs/day and not ferts for a week the problem really hasn't changed. I've tried raising my co2 injection rate, but any high than 1 bubble/second and my gourami start gasping and sitting on the substrate. Perhaps it's something else but I can't figure it out. All help/advice is appreciated!

[Tech Support PE]

Good day Merlin647,

I sympathize with your situation, I've been there myself! Balance in a planted aquarium, especially high tech ones, is a complex beast, but the good news is it's achievable with time and understanding. We'll get you there!

Our number one concept is going to be how balance influences plant health and algae growth.

The first thing you need to keep in mind is balance between light, carbon; in your case CO2, and nutrients. Think of a car; when you press on the accelerator the car goes faster but requires more fuel to do so and the more engine wear it causes. With planted tanks the light is the accelerator, CO2 is the fuel, and nutrients are the oil, coolant, etc that keep the engine running. The higher the light the faster your plants will want to grow meaning you need more CO2 and the nutrients your tank needs to avoid breaking down (plate death and algae) . You said that your CO2 is up as high as is safe for your fish, so we'll need to address light and nutrients.

Light- When it comes to light there are two main things to consider: intensity and photoperiod (number of hours your lights are on). The more intense the light, the faster the plants' metabolism is going to go. If you can't balance that with CO2 and nutrient input you'll need to reduce light intensity and possibly photoperiod. Plants are like people; they're only "awake" for a certain number of hours a day and require rest, in the form of no light. What you're going to need to do is find the balance between intensity and photoperiod that coincides with your plants' activity. With high intensity lighting this is usually around 9 hours per day; sometimes less and sometimes more, depending on the fixture, but is typically around 9 hours. This means your plants are only utilizing the light you're giving them for a portion of the day with the rest of it going toward fueling algae (light imbalance). In your case, I would recommend cutting light to about 50% output as that fixture is pretty strong and your tank's not particularly deep so light can penetrate the water fairly well. In addition, I'd set the total photoperiod to 8 hours with no light on after that. 24/7 lights are nifty and can make nice nightlights, but you're only benefitting algae having it on longer than your plants are active.

Nutrients (aka, Ferts)- I'm glad to hear you're using the full line of our nutrient supplements; aquatic plants require all of them to survive. This is especially important for high-light (high energy) tanks with inert substrates. High light intensity causes many forms of stress and increases metabolic processes that cause damage to plants, regardless if they're outside or in an aquarium. If you're not providing adequate nutrition then your plants can't do what they need to repair themselves. We see this as algae since the plants start leaking sugars and electrolytes into the water, providing food for for algae. This is why we often see algae on leaves in unbalanced planted tanks. Although plants are more than capable of taking up nutrients from the substrate, that can be a rate-limiting step as the plants are often unable to transport them to the stems and leaves fast enough to meet demand. This all ties together in the need to increase nutrient input. You say your NO3 is 10-20; that's perfect. What's your PO4? You want about a 5:1 ratio of NO3 to PO4. From my experience green spot algae (GSA) and green dust algae (GDA) are a result of insufficient phosphorus relative to iron. Can you tell me how much iron you're adding?

What are you adding for Ca, Mg, K, and S? These are all nutrients your plants need in large quantity.

Dissolved Organic Carbon/Compounds (DOC) and Eutrophication- In the world of aquatic ecology we use a term called eutrophication. This is when an aquatic system receives excessive DOC, N (NO3), and P (PO4), leading to uncontrolled algae proliferation and eventual death of aquatic plants in the system. Plants aren't able to take up DOC in significant amounts, but algae love it! In our tanks we primarily get DOC from feces, leftover food, and gunk in the filter. In an ecosystem sense our aquariums are highly eutrophic. The good news is by controlling DOC we're able to minimize algae growth and maximize plant growth. Assuming you're keeping your substrate and filter clean, you're going to want to add Purigen to your filter. I've been using it for decades and have found no better way of reducing DOC. I don't run an aquarium of any sort without it and strongly recommend you use it as planted tanks especially benefit a lot from its use.

That's probably enough for now so I'll leave you with this analogy. Think of a three-legged stool. When all the legs are the same length (in balance) you can sit and stand on it without issue. The second one of the legs gets longer or shorter than the others it tips over and you fall off. In a planted tank, each leg represents three things: 1- Light and Carbon balance, 2- correct nutrient input, and 3- DOC control/cleanliness. Once you get to the point where the legs are equal length your tank is balanced and everything will be a lot happier.

I know this is a lot to unpack. If you have any questions or want clarification, please don't hesitate to reply, I'm happy to help.

Kind regards,
PE

[ISHOUKI]

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