During the day there is enough natural light coming to the tank. For a period there is some sunlight as well.
So I only use the tank light for 2-3 hours in evening. Some days keep the tank light off as well.
Today I again tested the water in my tank:
Ammonia: same as 2 days back. Should be zero
So looks like the above parameters are now sorted and stable.
Somebody had advised me that I should re-mineralize RO water. Recent 50% water change was with municipal water but that also had a hardness of 50 mg/l (same as RO water). Next water change I can add tap water but that has 4.0 ammonia so not workable. Can anybody suggest me how to add minerals?
For fish from soft water you do not need to re-mineralize RO water. Considering what is in your two water sources, this would be preferable, straight RO if you can. The tetras and catfish are soft water.
A few quick thoughts from somebody who alters water params in one tanl regularly in a few other ftanks as needed to simulate dry/rainy seasons and who owns a portable RO/DI unit.
RO will remove a lot of things but not all of them. Most units have multiple modules which contain different media which should remove specific things. What modules one needs depends on the problems and desired end results.
So, the initial modules would be a sediment filter and an activated carbon filter in that order if both are needed, Th first one should be obvious as to what it removes. Carbon removes a variety of things to include these important to us ones:
Carbon removes a class of material called dissolved organic compounds (DOC). These compounds are produced by many different processes in the aquarium. The two major categories of organic substances that carbon removes are tannins and phenols. Tannins give the water a yellow-brown color. They are produced mainly by the breakdown of plant material, but there are other sources too. Phenols give a fish tank that characteristic “fishy” smell. Carbon can also remove chlorine and some heavy metals through other processes.Carbon does not remove ammonia, nitrite or nitrate from water. It also does not have an effect on water hardness or alkalinity.
Next inline would be the RO membrane module. This removes a lot of stuff, but not everything. It wont remove everything but it does remove a lot. However, there is one more module one may wish to include and I do so in my small 3 module system, And that is a DI module. DI stands for deionizing and that means the removal of ions. Ions are electrically charged atoms or molecules found in water that have either a net negative or positive charge.
The Ions we all know would be Ammonium NH₄⁺ Nitrite NO2− Nitrate NO3-.
Basically, a system which flows input water --> sediment module -->carbon module-->RO module-->DI Module should produce almost pure water. There are more module one could have if they are needed. I do fine with carbon-->RO-->DI but I have to backwash my init to flush the sediment it catches. It is not a lot but enough that I would get a 4 stage unit the next time were there to be a next time. I have well water and do not use dechlor. But I need soft acid water for one tank.
So, your solution may or may not be making water to specific parameters. it is not simple nor easy to do. The chemistry is all intertwined. Hardness, pH, KH, GH etc are not isolated from each other in terms of what they can affect.
The best advice I can offer is the less meddling with parameters that one has to do the better.
Once you change your parameters, you will also need to change them for the water change refill water.
So an update, and a problem!
Yesterday I tested the water:
Ammonia 0 - 0.25 (maybe slightly increased in last 4 days, but still well under 0.25)
Then I changed 50% water. Added Prime to new water and then added some hot water to increase the temperature to be close to aquarium water. New fresh water read:
Then, since most of the fish in my tank (20g) had died (left with 5 glofish tetras with one of those 5 showing the symptoms (gills thickened and deep reddish, unable to swim, floating at top) and would not live beyond a few days) and parameters were kind of stable, I added some new fish yesterday after water change. I added 4 new glofish tetras (2 same size as existing ones and 2 relatively smaller) and 2 copper gouramis (looked like thick lipped gouramis). I will add a bristlenose after a week or so to help with the algae.
In the bag all looked fine. Bag was in my tank water for 30 minutes then opened the bag and put my tank water in the bag (to double the water in the bag) and then took out the fish by hand and put in my tank. All were fine. Within a few minutes I notice one of the new small tetras skimming the top of the tank and would not go down. After maybe 2 hours it couldnt swim properly and died. Rest look happy.
Does something like this happen? Water parameters seem to be okay and Prime was also added in sufficient quantity.
Now I am planning to add some hardy live plants in the tank. I have gravel substrate about 2" at the back and 1" at front. Should I add more gravel? For the plants I will need to use root tabs and liquid fertilizer. Planning to put Amazon sword / Vallisneria / Ludwigia / Java Fern, etc.
Hopefully this will bring out the best in the tank. Any suggestions please?