CO2 Requirements

[PrincessFish]

Hi all,

       I have been struggling to understand and balance my planted tank for over a year now.  For the longest time I battled algae, mostly the brown mucky stuff initially and then black hair.  Now it is under control but not all gone.  My questions are around the use of CO2.  For the past two months I have been running two DIY Hagen systems in my 25gal (refresh 1/week).  On top of that I am now up to 4 full capfuls / day of excel and still can't get my CO2 up over 8.  Having read frequently on this site that more than one DIY system is not needed for a tank this size I am confused about my situation.  I change ~ 30% of the water weekly.  All my parameters are almost non-existant including phosphate - even nitrate is around 5 (perhaps low?).  I have a double T5 light system providing almost 2wpg of light and leave it on 10 hours/day.  Does this make sense?  I want to get rid of the algae completely and have a lush green tank of the kind I see here that so many of you have.  Any advice would be most welcome!!
        Thanks in advance 

[matt]

You might want to look into adding fertilizers into your tank. Read up on tom barr's estimative index method. It'll give you a pretty good idea about ferts. What you'll have to add to your tank is nitrate, sulphate, phosphate and trace elements.

[dan2x38]

Couple questions... What plants? How tall is your tank? What substrate & how deep? Any ferts besides Excel? What type of filter do you have? Do you leave the water level low? Any airstones or bubblewands? Near direct sunlight? How much how often do you feed? What & how many fish? You said you change CO2 once a week... is that both bottles at the same time? How is the CO2 diffused?

You have enough light for sure depending on the tank depth. With those lights the plants should grow quickly. So the plants use up all the nutrients very quickly including one main one CO2. The plant's growth slows or stops since they have a complex cell structure. Now algae is a simple cell structure so it is able to take advantage of the light and CO2 along with the small amount of nutrients available from the fish food & fish waste. Hence an algae bloom or battle. The NO3 being at 5ppm is low you should be adding NPK & trace or something like Seachem Flourish.

DIY your CO2 with high lighting is a tough balance. I am doing it with 2 DIY bottles & 3.5wpg lighting. I alternate changing them a week apart so every 7 days there is a new bottle producing. Some times I will change alternate bottles every 5 days (total 10 days per bottle) when I notice a bit of algae on the glass. My readings are around 23ppm. I keep my water level high with low splash from an AC filter. I run my CO2 diffused through a spraybar under the water to disperse it. I have no airstones or bubblewands to prevent gassing out my CO2. I feed twice a day just enough for the crew to eat in a couple minutes. One day a week they don't get feed. I have 3 cories & 3 YoYo loaches to clean the bottom. This tank grows great coloured plants and fast.

I tried the Tom Barr EI method but with unstable CO2 levels I ended up with a lot of algae and had to cut everything back. It took me 4 months to get things growing normally again. I use dry ferts but I use a kind of PMDD method... I mix per the Krib's recipe for that and dose by observation now. I watch any algae forming on the glass. When that shows I change about 40%-50% of the water then dose macros, the next day micros.

Hope this is of some help...