It has been a while since the last update. The arowana is growing well, but the plants can do better. Frankly, the main reason for the lack of updates is the less than ideal condition of the plants and algae situation.

I’ve been getting an alga that forms a film on the leaves and hardscape, then dies and turns brown and hard. Also getting the green dust algae (GDA) on my glass. No one apparently has found a good solution for GDA besides lots of Bristlenose Plecos (BN). WIth my aggro arowana, more algae eaters is not really an option. Would really love to put in 10 more BN, or 2 platoons of Otos.

Further compounding the problem, I modified my CO2 dissolution system. I had a custom-made CO2 reactor in-line with my sump return pump. The dissolution rate wasn’t as good as I wanted and figuring that it could be due to the flow being too strong, I removed it and used a smaller dedicated pump on the reactor. From then, plant growth in the tank got worse slowly, but I didn’t realise it was due to low CO2 till later. Because of the way the reactor was placed and without the high pressure of the return pump, it had a harder time dissolving CO2 and at the same time, encouraged any gases in the water to evaporate out. I’ll explain in detail in a later post with illustrations.

In hindsight, the poor growth was obviously due to the drop in CO2. The Staurogyne repens, which were growing beautifully before, slowly succumbed to the weird brown algae and died bit by bit. The red tiger lotus also produced smaller and smaller leaves. The Bolbitis were still growing new leaves, but the brown algae were smothering the leaves as they grew. Instead of considering CO2, I went looking at fertilisation problems. The deterioration was so slow that I neglected to consider CO2 as the main cause.

During that time, I noticed a much bigger gas pocket in the reactor than before. I kept wondering why. I even had to reduce the CO2 injection rate. Eventually, after months, I guessed it might be due to the outlet being at the bottom of the reactor and hence the water level is always trying to drop. This results in low pressure inside the reactor, reducing the ability of the CO2 to dissolve. Acting on that hunch, I turned the reactor around and reversed the flow. Lo and behold, the gas pocket reduced significantly. So I’ve set the CO2 injection rate back up. This resulted in a slightly better growth from the S. repens and lotus.

I decided I wanted to further improved the CO2 distribution. Some time back I had read that placing a spray bar along the entire length of the back of the tank, pointing forward is one of the best ways to distribute CO2 all over a large tank. So I went and got some PVC pipes, DIY’d a spray bar and installed it. After 3 weeks, there is noticeable better growth from parts of the S. repens.

Unfortunately, I think the S. repens has deteriorated to the point where most of it does not seem to be recovering. I’ve decided to remove them in the near future and plant a new lawn and other plants. Going to remove the white sand bed, which is now brown, and replace it with Aquasoil and a new lawn.

I tried to re-tie the Bolbitis this past weekend but discovered lots of dead rotting rhizomes (despite the constant new leaves). Decided to throw out the lot and get new ones. As a result, just barely a week later, I noticed that the brown algae on the rocks near the Bolbitis is being slowly cleared away. I’m guessing that the rotting Bolbitis was feeding the algae in the area and now that it’s gone, the algae growth has slowed or stopped and the SAEs can out-eat it.

So, hopefully, in a few weeks, I can start sharing new pictures of the tank with nice plant growth. Wish me luck!