Water Acidity in planted tanks and it's impact?

[Allan Asis]

Hi guys,

Although my tank's been running for 3 months now I only found out recently that my pH has been hovering around 4.5-5.0pH (after using SERA test kit) because I've been using API pH test that caps it at 6.0pH.
I believe most plants if not all like acidic waters but is 4.5pH too low?

for 2 weeks now i've been diligent on cleaning the tank of decaying plant leaves/stems/roots they count as organic matter that when broken down can adds up to acidity in the water (correct me if i'm wrong here).
Also water change of about 40-50% every 3 days yet the pH just comes back to that 4.5-5.0 range the next day.

Do liquid fertilizers such as seachem flourish line increase acidity in water as well?

Is this something I have to be concerned at? My tank has suffered plant decay since last month and after dosing fertilizers (seachem flourish line), they rebounded but still in progress.

As for algae, since the plants started to decay last month, I noticed diatoms coming back and covering older leaves and stems. green hair algae also started to appear but probably due to increase in iron from my dosing.
do water pH have any correlation with presence of a certain type of algae (in my case green hair and diatoms)?

Thanks!

[Urban Aquaria]

Its natural for the pH of a tank to steadily decrease as the organic compounds build up over time (especially so in planted tanks)... in your case, all the rotting plant matter are contributing to increasing organic waste that the beneficial bacteria have to handle and this increased nitrification process has an acidifying effect and lowers pH.

Its similar to blackwater streams with lots of rotting leaves and branches in the water, the water pH typically hits 4.0 levels, some fishes thrive in those environments.

Fertilizers don't affect pH significantly so no issues with their usage.

I guess once your plants recover and the rate of them melting decrease, the system will gradually stabilize itself and you'll see the pH maintaining at more moderate levels. Cleaning your filter and rinsing the bio-media and sponges to dislodge all the trapped detritus also helps alot too, alot of the rotting plant matter (aka waste bio-load) is usually trapped in the filter.

The algae growth is mainly due to the influx of excess nutrients and poor plant health, as the plants deteriorate their nutrient in-take decreases and their rotting leaves return ammonia and nutrients back into the system, hence the algae takeover and feed on them. Its more to do with excess nutrients rather than pH.

[Allan Asis]

Its natural for the pH of a tank to steadily decrease as the organic compounds build up over time (especially so in planted tanks)... in your case, all the rotting plant matter are contributing to increasing organic waste that the beneficial bacteria have to handle and this increased nitrification process has an acidifying effect and lowers pH.

Its similar to blackwater streams with lots of rotting leaves and branches in the water, the water pH typically hits 4.0 levels, some fishes thrive in those environments.

Fertilizers don't affect pH significantly so no issues with their usage.

I guess once your plants recover and the rate of them melting decrease, the system will gradually stabilize itself and you'll see the pH maintaining at more moderate levels. Cleaning your filter and rinsing the bio-media and sponges to dislodge all the trapped detritus also helps alot too, alot of the rotting plant matter (aka waste bio-load) is usually trapped in the filter.

The algae growth is mainly due to the influx of excess nutrients and poor plant health, as the plants deteriorate their nutrient in-take decreases and their rotting leaves return ammonia and nutrients back into the system, hence the algae takeover and feed on them. Its more to do with excess nutrients rather than pH.

Thanks for the explanation UA!
I guess it's just a matter of time before things get a lot better in my tank so long as I keep up with the water change and consistent fertilization. for now I will monitor pH but will not worry about its low value and when I start noticing it staying higher than what I am measuring now I guess it's a good sign that the biological filter is catching up with the decaying organic matter in my tank