Elatine triandra and nitrates

To get my tank to recover, I am replanting the tank in phases. Starting about 4 weeks ago with Elatine triandra which is fondly known as Ah Pek Plant (APP) in Singapore. Once planted, the Elatine immediately flourished. Elatine is a very fast growing plant and is a nutrient hog. With lots of fertilisers (including CO2) and light, it grows very fast. At the same time, once fertilisers are lacking it melts very fast.

At the second week, I tested my NO3 just to see if it has reduced and it was still in the 40-80 ppm range. From the start of the tank till now, I’ve never had less than 20ppm NO3 in the tank even though I don’t dose NO3 except for a span of a few months last year.

By the third week, I had to trim the Elatine as they had started to overgrow my low rocks and looking rather unsightly.  Hopefully, trimming would encourage more side shoots and creeping growth rather than the upward growth till then. Algae on the glass had also noticeable reduced. But, I noticed that the old leaves were starting to yellow and melt. It was still minor, so I decided to just wait and watch. Maybe it’s just new tank syndrome? The symptoms indicated either N or P deficiency. I dose P, so that was eliminated. My tank supposedly has high N, so I disregarded that. I have already maxed the dissolution capability of my CO2 reactor, so that’s not option anymore… plus growth was excellent before, so can’t be CO2.

This last weekend, the fourth week, the Elatine looked really bad. Large patches had melted completely. This 2 days, they continue to melt…

I dose everything (P, K, CO2, trace and Fe) that the plants need to grow well, except N. So today I tested for NO3 again… lo and behold, ZERO nitrates! And it correlates with the symptoms of yellowing leaves melting from tip to stem. The Elatine sucked up all the NO3 that has been above the 20ppm range all this time in about 4 weeks.

Admittingly, I may have been an accomplice. In trying to fix things with the tank, I have in the last 2 months, progressively made major changes and done major cleaning in the tank:

  • Removed the white sand foreground.
  • Vacuumed and trimmed the algae infested plants, especially the big dirt trap mass of Java fern.

I further suspect that my tap water which used to come with about 20ppm NO3 may not have NO3 anymore. This needs testing to confirm.

Fortunately, I still have my NO3 solution in my cabinet and quickly made a dose. Let’s see what happens to the remaining Elatine in the coming weeks. It should recover quickly as it’s a very fast growing plant and I still have about 60% of the lawn still viable.

In the medium term, I will replace them with Staurogyne repens, but might keep a small patch as the proverbial “canary in a coal mine” for nutrient issues. It’ll be helpful as a indicator plant when the tank stabilises and I start tweaking my fertiliser dosages down.

Bouncing Back

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 lack of updates is the less than ideal condition of the plants and algae situation.

I’ve been getting an algae 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 had 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.

On hindsight, the poor growth was obviously due to the drop in CO2,. The Staurogyne repens, that was 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 was still growing new leaves, but the brown algae was smothering the leaves as the 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 a 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 rhizome (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!