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. It grows very fast with lots of fertilisers (including CO₂) and light. At the same time, once fertilisers are lacking it melts very fast.

In 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 few months last year.

By the third week, I had to trim the Elatine as they had started to overgrow my low rocks and look rather unsightly.  Hopefully, trimming would encourage more side shoots and creeping growth rather than upward growth till then. Algae on the glass had also noticeably 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 an 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. These 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 an indicator plant when the tank stabilises and I start tweaking my fertiliser dosages down.