Hello Ms. Monisha Hyder

If the contamination is already established ion the mature fronds of the red algae them it might be too late to rectify the problem on the existing batch. However, selection of the starter plant tip is one of the most crucial phases of the culture of Gracilaria as if done correctly in a sterilised environment, almost 90 % of the epiphytic contaminants can be avoided. Following the selection and isolation of the tips as starter plants, if any contaminants do exists then they can be placed in near dark or very low light conditions to eliminate particularly green algae, as red algae due to the presence of xanthophylls and erythrins are better adept at photosynthesising at low light. Physical method such as gentle scrubbing with cotton balls and cotton swabs is also known to remove epiphytes at early stage of establishment.

In addition to what I have just mentioned, you can also consult the New England Gracilaria culture handbook for a better understanding of the culture techniques.

Regards,

Dr. Abhishek Mukherjee

Thank you Mukherjee sir,

We almost regularly cleaning those epiphytes manually by brush and needle. but for mass production of germlings it is soo difficult to do and avoid these. so if any posible decontamination method by chemical agents it could be so helpful to avoid. And thanks for your suggestion sir. i could try with light intensity.

Enteromorpha produce "Swarmers" which settle on substratum during growing vegetative cycle & are usually found in the upper layers of water. On the other hand, Gracillaria can live & grow in diffused light at lower layers. Therefore keep the red alga at lower levels & after change of seawater, allow swarmers to come to top layers of water & then skim off the top layers of water by a flexible tube taking care to see that slowly, only the superficial waters are skimmed off. Carry this out a few times by which almost all of the swarmers would have been eliminated.

Alternatively store fresh seawater in a total dark place for a month & use this for culture purposes.

Another way is to dilute 300 parts per thousand brine with distilled water making it to seawater salinity & use this water as culture water, whereby ensuring nil contamination.