It depends on the marker you want to amplify! If you are trying to amplify the DNA barcoding sector (COI), I suggest you use the Folmer primers - LCO1490/HC02198.

Thank you sir,

I already follow Folmer primer for COI. some species especially Chrysaora could't get  result  by the use of this primer.  I am trying to repeat amplification with this primer to confirm better result.

Curious, because I never had problems to amplify Pelagiidae with these primers. How are your extractions?

Sir,

I am mistaken in any step of isolation. Because few samples of Pelagiidae species DNA isolated earlier with good result. I have extracted DNA from the tentacles, bell margin and gonad using (Orgin) Marine DNA kit. Please give me some suggestion to get a good result.