SIBIETA wrote:
...
About the water changes, i think you are right i do too much water changes,
but i need to vacum the gravel some time so, what do you think if i make 1
liter changes every day an 50% changes every week?.
...

I don't understand why you feel the need to make such intensive water
changes. My setup, for example, is very similar to yours - I have a
well-planted 5.5 gal tank with 26W of light (two independently
controlled 13W bulbs) and DIY CO2 injection. 26W is a lot for a
freshwater 5.5 gal tank, so I keep only one 13W bulb on for 12 hours a
day, while the second one comes on for only 1 hour in the middle of the
day. (I used to turn it on for 5 hours a day, but it seemed to lead to
staghorn algae problem). I change about 30% of the water every week and
try to carefully vacuum the gravel (where I can reach it) every other
week. The tank is doing fine.

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Best regards,
Andrey Tarasevich