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Discussion Starter · #1 ·
What are the effects of low pH on plant growth and nutrient utilization?

I'm asking because of an odd observation in my own 20g.

I've been trying to read my plants a lot more lately to tell what they need and how fast they go through ferts. My stats are below, but I've noticed that ludwigia peruensis grew in some white leaves after I moved the tank to another room (1.5 weeks ago). I managed to keep 70% of the present water, but they substrate was completely disturbed. Colorless leaves... I believe is a sign of calcium deficiency, yet I have very hard water. I've tried dosing what I can without overdosing. Even so, my growth is stunted throughout the tank. Why? I just third water change to bring the pH back up to norm, got it to 6.8 and in an hour my plants are pearling.

Does pH affect how plants uptake nutrients?

pH was 6.4-6.6 for around 2 weeks
KH 6.5 degr.
GH 11 degr.
Nitrates/Phosphates kept at good levels... 10-15/1 respectively

4x20W T12 full spect bulbs 12hrs/day
Magnum 220 Canister
Plant Gro Co2 Natural System w/ ladder diffuser slightly modified mixture
1 bag Oxyn Sand
1 bag EcoComplete

Fish (heavy load):
1x Angel (small 3" nose to tail tip)
Several Mollies
2x small Khuli
4x Pristella Tetra
3x Neon Tetra
2x White Tetra
1x Glofish
1x Amano Shrimp
TONSx Malaysian Trumpet

Wisteria: Hygrophila difformis
Limnophila ‘hippuroides’ (Limnophila hippuroides)
Ludwigia Peruensis (Ludwigia peruensis)
Rotala Magenta (Rotala macrandra v. 'narrow leaf')
Tiger Lotus, Red (Nymphaea zenkeri)
Moneywort: Bacopa Monnieri
couple random long leaf swords

· Premium Member
7,439 Posts
You apparently use your test kits to determine how much nitrate and phosphate to add. If you do that it is essential that you first calibrate the test kits, and recalibrate them every month or so. Otherwise you really don't know how much of each nutrient you have in the water, and you may be very short of one. Test kits do go bad, even when they initially work well, with they don't always do.

Your description of the problem makes me suspect inadequate NPK or CO2 (Excel) fertilizing.

I realize you asked about pH. As far as I know pH is not an independent variable. It changes a bit as other chemical changes occur in the water, most notably the concentration of CO2 and the KH. Plants don't seem to be affected by pH unless the cause of the particular pH is something that does affect the plants.
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