Hi,

Some of my plants are having a hard time to fix in the substrate (ammania gracilis, ludwigia arcuata and ludwigia pantanal). Their stems rot on the substrate, and the plant either floats or keeps fixed by some upper root that ended up reaching the substrate.

My substrate is eco-complete (7 month old). My ph is around 6.2 - 6.8 (after and before co2 injection).

Is there a reason for that (acid soil)? Or is this something that may happen and I need to try re-planting stems? Because eventually I get some of them stablished, but I would like to avoid this problem.

Thanks,
Evandro.

Have you been adding enough KNO3?

Regards,
Tom Barr

I think so. However, NO3 is something that is consumed on the day I add it. Next day, I will see almost an unreadable level of it.

My tank is 20gallons and I add on saturday/monday/wednesday:

10ppm NO3 (30ppm total)
20ppm K (60ppm total)
2ppm PO4 (6ppm total)

On sunday/tuesday/thursday:

5ml seachem trace
4ml seachem iron

96watts turned on 9.5 hours a day.

60% weekly water changes.

Thanks,
Evandro.

96 watts for 9.5 hours a day on a 20 gallon tank!! I think your plants are being driven to consume all of the nitrates almost immediately after you dose them, then they starve for two days. Are you dosing phosphates too? If I were to try that much light, and I won't, I would switch to dosing daily. I would take the weekly EI dosage of each nutrient, divide it into 7 equal parts, and dose every day, both the macro nutrients and the micro nutrients. Then, if I still had your problem I would increase those dosages by at least 50%. Trying to adequately fertilize a tank with almost 5 watts per gallon of light is different from dosing a 2 watts per gallon tank.

A simple solution would be to cut the wattage in half.

GH is added?

I've seen a few plants rot due to low CO2, but mostly due to lack of macro nutrients.
And only with a very few species for both.

I'm not so sure it's a simple thing either.

Also, you might just consider vacuuming the area beneath the plants.
Be very careful replanting stems, be gentle as you can be.

Regards,
Tom Barr

My water is relatively hard - 8 dGH; KH is 2.5.

I forgot to mention that I also add 5ppm Mg with the macros (3x a week).

Now that you mention NO3 and CO2...

I think I should increase CO2 a little, because ludwiga arcuata has leaves a little twisted, as if some nutrient is lacking. In the last 2 weeks I have already done that and this problem reduced, but is not eliminated though.

I will increase CO2 a notch and also add a little more NO3 (spread over the 7 days) as VaughnH suggested.

I will do some experimentation on the photoperiod as well.

Thanks,
Evandro.

Don't forget the phosphates. Plants can't use the other nutrients if they don't get adequate phosphates. EI is a good guide for this.

Ok. I currently add 6ppm over 3 days and it seems that the phosphate levels are stables, i.e. they don't disappear as NO3.

Anyway, I will keep an I on that.

Thanks,
Evandro.

They both should go down rapidly over 3 days unless you have a high fish load.

Suspects: test kits are not calibrated.

Regards,
Tom Barr

After working on this issue, I found that ludwigia arcuata and also ammania gracillis stems were rotting on the substrate because its nutrients were depleated.

I used eco-complete but after 6 months with no solid fertilizer the substrate should be lacking nutrients and plants could not fix.

I added solid tablets all over and they don't rot any longer.

Thanks,
Evandro.