Growth of algae in hydroponic rice is not desirable ,since it will consume dissolved oxygen and increase the biological oxygen demand , thereby , facilitating the suiffocation of rice roots. Some toxins are also produced , which may dmage the rice plants in due course of time. The algal grwoth will also consume the nutrients to weaken the plants.

UV sterilization can be an option to eradicate planktonic algae.Traditional barley straw rafts have been known to control algae in large scale hydroponics as it has been effectively employed in aquaculture ponds since many years. If possible them Ceratophyllum demersum can be grown to compete with algae through the production of allelopathic chemicals but it is also a nutrient hog. Small amount of algae in actuality might be beneficial since they can provide the cultivated plants with growth hormones.

A compound of ammonium sulfate and aluminium sulfate (commonly called alum) has properties that could inhibit algae growth and has been successfully applied to reduce ammonia formation in litters and also to reduce phosphate solubility < http://agebb.missouri.edu/murice/research/mrf020.php >.

Dear Chandan kumar Gautam

You can use a manual rotary weeder. it is very easy to design and build and bring amazingly benefits for the rice plant. Not only controlling weeds but also increasing the production yield.

Please check the links below:

- chrome-extension://oemmndcbldboiebfnladdacbdfmadadm/http://sri.ciifad.cornell.edu/countries/india/extmats/SRIWeederManual06.pdf

- Article Field Performance Evaluation of Power Weeder for Paddy Crop

- chrome-extension://oemmndcbldboiebfnladdacbdfmadadm/http://www.iai.ga.a.u-tokyo.ac.jp/j-sri/meeting/sri-uphoff-sato.pdf

Wish you all the best

Dear Chandan, UV use is one of the most effective way, although it is expensive. Try to use chlorinated water and avoid direct lighting both sunlight or artificial light.

Hope this helps.

Regards,

Mohammed