What is causing necrosis in my plants?

[LabTest57]

A 160 to 240 gallon freshwater aquarium; fish load : 23 (3 to 4 inches each fish); 4 mechanical filters, and one trickle filter w/ drip-tray and 950 gph pump; water agitation: very high for high levels of oxygen; excessive black algae growth; 2 amazon sword plants, 1 onion plant... rest of them dead
:(

Water paremeters:
pH 7.2
kH: 90 ppm
gH: 100 to 150 ppm (increases because of water replacement every week from evaporation)
Ammonia: 0
Nitrites:0
Nitrates: 20
Temperature: 85 degrees fahrenheit
Feedings (for fish): 2 to 3 times a day.
Water replacement from evaporation: 10 to 15 gallons a week (pH 8.4, kH 120 ppm, gH 80 ppm)

I would like to know the type of deficiencies (as I cannot test for most of them) a plant can experience that will result in necrosis?

Most of my plants are having necrosis on one leaf and/or stem at a time (older leaves brown-up at veins first then entire leaf, while younger ones have browning on the tips).

I've made another 50% water change to bring down my salt and chloride levels to safe levels for my fish and plants. I continously add anywhere from 20 ppm to 60 ppm of potassium to my plants, which I believe is the main cause for the necrosis, however, this doesn't seem true now that all my plants have necrosis.

Could this be from a mix of other deficiencies like iron, manganese, and other minor elements? Is it from the effect of the high levels of salt that were present in my aquarium for about a month?

Someone told me this could be from high phosphate levels that occur from decomposing plants and food, however, the large water changes I make every month should reduce the levels a lot.


Also, my plants are experiencing some extremely stunted growth and have black or brown algae growing on them.

[Tech Support AN]

Sounds like a pretty nice set-up, except for the dying part. :-( The first thing that stands out to me is that you feed your fish 2-3 times daily. That might be a contributing factor to the algae growth, as this is just building up excess dissolved organics. You may want to cut back your feeding and see if this helps to reduce the algae growth. I would also test your phosphate level if possible and continue doing the water changes. The issues that you are seeing with your plants could certainly be a mix of different deficiencies or quite possibly you are still seeing effects of the high salt and chloride content that was in your water. Both sodium and chloride are not rapidly depleted elements in a planted aquarium, and, in the case of chloride, can do more harm than good. I am not sure if you have ever seen our chart with the different functions and deficiencies of all the major and minor elements needed by plants, but I will post it below. The link will actually take you to the Flourish product web page, but then click on the chart link in the first paragraph.

http://www.seachem.com/Products/product_pages/Flourish.html

I hope you find this chart helpful and please let us know if you have any further questions.

[LabTest57]

Thanks for the chart, but I've seen it before.

The only time that I've ever seen my plants never die was when I used to add well water to my aquarium. It had very high levels of iron, but it also had a gH above 600 ppm, which is not good. This was like 6 months ago, and I used Flourish at the time as well.

I stopped using well water because it gave my fish gill flukes and ich. Even treating the water with sodium hypochlorite for a few minutes and dechlorinating afterwards did not solve anything. I had to use my tap water, and kept adding Flourish. Slowly my plants started having chlorosis and stunted growth over the next several months. That is when I was trying to find out what specific nutrient could boost my plants growth, you guys told me potassium does a lot for most plants,etc. Now, I'm dosing with Potassium at a rate of 20 to 60 ppm per month, but my plants were getting worse and worse.

If my well water is the key to my plants survival, meaning it might contain a lot of nutrients,etc., I would have to find a way to oxidize/kill any parasites and bacteria, and lower the gH significantly.

If I do a 25% water change and add well water, that will increase my gH plus 150 ppm. So if my current gH is about 100 ppm, I will have 225 ppm afterwards. [100 minus 25 plus 150 (600/4) = 225] is my calculations correct?

[Tech Support AN]

I believe that your calculations and general thought process here are correct and it will definitely be in that ballpark. Also keep in mind that the potassium that you are dosing is going to contribute as well.

[LabTest57]

Is it wise to increase, temporarily, the kH over 600 ppm with sodium carbonate to cause calcium carbonate precipitation in order to lower the gH levels. Then, I can add acid to lower the kH and pH afterwards.

Of course, this has to be done in a tank that doesn't contain any ornamnets, gravel, filters, nor fish, so that I can clean up the calcium carbonate build up after I add the water to my main tank.

I was thinking that if I cause such a huge precipitation, that iron and other metals can precipitate as well. Is this true?

[LabTest57]

I've been doing some research on the type of plants and fish I have to see if I can find a common pH and water hardness level. Actually all my fish are able to tolerate acidic to neutral pH and an average gH level of 80 ppm. Amazon sword plants do well in soft water and acidic conditons, so I'm going to try it out.

I will buffer my water to have at least 40 ppm kH, 80 ppm gH, and a pH range of 6.4 to 6.8.

I will let you know if anything comes up (i.e. better growth or worse...) in the next month or so. :)

[Tech Support AN]

By causing such a drastic precipitation, you will definitely see your GH levels decrease, as well as, iron and other heavy metals. This is going to cause a huge cloudy, white mess, that will need to be removed/cleaned completely before adding any acid back to the tank, as this will just re-dissolve everything back into solution, negating the initial reason for doing this. Essentially, you could just use a pillow softener to bring down your GH levels, but I realize you like to experiment, so more power to ya! Let us know how everything turns out! 8-)

[LabTest57]

Well, I've thought about doing this in a 35 gallon plastic tank, and just add over 5 ounces of baking soda, but increase the pH past 9.0 so most bicarbonates can convert to carbonates.

Still looking for other ways to lower gH...nope I guess I would need exchange resins and use potassium chloride. The thing is, I'm trying to lower gH but retain important metals like iron.

If I cause calcium carbonate to form, is it possible to lower the pH down to 6 (temporarily) to cause any precipitated metals to become soluble again? Then, the calcium carbonate should stay at the bottom of the tank, while I pour the water in another tank to lower kH and pH and not dissolve any calcium carbonate. Is this possible?

[Tech Support AN]

If you lower the pH, everything, including the calcium carbonate will begin to go back into solution. I read that even a pH of 7.0 can dissolve up to 15.9 g/L calcium carbonate. This is because your water is becoming more acidic the lower you go. You could use RO water to reduce your GH and then supplement iron if needed....?

[LabTest57]

Oh well, I guess I have to wait next season to see if my well water's general hardness drops to at least 200 to 300 ppm. Last year it averaged around 300 ppm. Durring the summer and mid-fall it usually rains a lot over here, and that is probably why so much limestone gets dissolved and flows through my well.


Well, I'm going to just change the chemistry of my aquarium water to make it similar to amazon waters, because of the type of fish and plants I have (e.g. angels, guoramis, tetras, amazon sword plants,etc.)

My targeted parameters will be:

pH 6.5
kH 2-3 degrees
gH 4-5 degrees
no soluble nutirents for plants, however, I will try using Flourish tabs for roots of the plants instead.
I will also up the gallonage in my aquarium by 10 from the water-level-control-tank I have to lower surface agitation from my pump's return jet.


Some questions...

At what pH do bicarbonates convert to CO2 completely?
How many Flourish Tabs do I add per plant?
How long does one tab last in acidic waters?
Is it possible for the roots of the plant to extract nutrients, if the tabs are placed 3 to 6 inches away from the plant?
I have 3.5 inches of gravel (height or depth). My plants are planted 1 inch deep in the gravel. How deep should I put the tabs into the gravel?

Is it wise to use Potassium chloride to add potassium to my plants? I know chlorides are only beneficial to relieve nitrite toxicity, but the amount of chlorides in potassium chloride compared to salt is really low.