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[APD] Re: Nutrients, Water Changes, Etc.

As a planted tank "enthusiast" (I refrain from applying to myself the venerable terms "aquatic gardner" or "aquascaper") who lurks happily somewhere between Barr Level 1 and 2, I am chiefly interested in a small number of tanks that look good over a long haul with a minimum amount of work. A few observations for what they are worth:

1. High nitrates (>100 ppm) seem to slow growth to a crawl. I had two tanks that went way over the top in nitrates (let's not discuss why, OK?). As soon as I brought the nitrates down to below 40 ppm, plant growth resumed with a vengeance, especially my dwarf hygro which sprouted dozens of side shoots and turned into a shrub. Fish seemed to appreciate it too. Lesson: watch those nitrates, especially in high fish load tanks.

2. I'm wondering about long-term build up of residual salts due to regular dosing of fertilizers. Most of the nutrients we add are chloride or sulfate salts. While the potassium, magnesium, etc. are utilized by the plants, the counter ions are not (except in the case of KNO3 or KHCO3). Presumably, there will be a long term build up of sulfate and chloride salts in the water column. A 50% water change will not offset the additions. Which leads to a thought: For long term stability, perhaps a huge water change, say 50% daily for a week, a couple of times a year, might help to "reset" the tank to its starting parameters might be in order. When I battled a green water plague in a 29 gal, I did daily 15 gal changes for two weeks. The ensuing plant growth was remarkable. I've noticed that over the years, my tanks seem to "slow down" in terms of growth and vitality. Should we be thinking in terms of a "rainy season" for our tanks to flush them out?

3. Recently observed an interesting nutrient deficiency. My water is fairly hard (13 dGH). My L. repens was showing signs of Fe deficiency (correcting the high nitrates caused the Fe to plummet from 1 ppm to almost undetectable). After correcting the Fe, the plant was still having trouble - rapid, though pale pink new growth, brown holes and yellowing of old leaves with premature leaf loss. After a bit of netsearch, I discovered that L. repens is sensitive to high Ca/Mg ratios. One change I had made was that I was dosing Fe/traces using Homegrown Hydroponics chelated trace mix, which has no magnesium. The addition of a small amount of epsom salts corrected the situation almost overnight. The new growth is turning red with some green. Thought: Even with hard water, you might run into magnesium deficiency if the Ca/Mg ratio is not right.

Your thoughts are always appreciated.


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