I would leave the aeration on, especially given that the aquarium is not heavily planted. Aeration is not used when an aquarium is heavily planted with fast growing plants, provided with significant lighting and CO2.

If your aquarium is planted with slow-growing plants like Anubias then leave your aeration on.

Joseph

Do you have fish in the tank? if so, leave the aeration on. None of the plants you mentioned are fussy about CO2 and will not provide enough oxygen for the livestock (depending on how heavily stocked it is).

If you have no fish in the tank then you should add a few because the plants will need nutrients from their waste and CO2 from respiration to use in photosynthesis.

yes i do have fish in the tank...it is moderatly stocked and i feed 2 times a day.all plants are very slow growers except the hornwort.i asked about aeration because i read in the net that  aeration will put away due to surface agitation the little co2 that is present in the tank(co2 produced by the fish)Thus depleating the tank from co2.i do not know if this is true.

do you suggest that i make some simple diy co2 to help plants grow better and healthier?or shall i dose just some liquid fert like sera florena?

Spiru, hornwort grows quite fast even without CO2, being a bit of an exception. It grows faster if kept close to the surface, which is a good idea as it helps fighting algae. If you want to provide yeast-based CO2 go ahead, but it isn't strictly necessary for your plants. I would leave the aeration on in any case, even though it will lead to a reduction in CO2 levels.

Remember that most books and information about plants are mainly written with fast-growing plants in mind, usually assuming that the aquarium is heavily planted and sometimes with low stocking levels in terms of fish. You will find rather little information about aquariums stocked with slow-growing plants.

Joseph

yes in fact i do not have algae..or very little.i keep the hornwort floating but it is a bit unsighty dancing about with water current and sticking to anubias.,and it doescover a lot of light altough i trim it fortnightly.i also have java moss which in 2 months only grew one inch.maybe lack of light?yesterday i also begen to fertlize with sera florena

You don't need CO2, it will cause more hassle anyway what with the fluctuating water conditions when you forget to replace the mixture etc and it will have a very small effect on the plants you have anyway.

Lighting is also probably not the problem anyway. Java moss is a slow grower and needs very little light. It tends to spread fast though as although it grows slowly, it is very adept at reproduction and small pieces will start to float around and stick to different objects in the tank and start to grow there. Regarding fertilizer, for the java ferns, hornwort and anubias, a liquid fertilizer will help but apart from that really you don't need anything else.