Hi Daniel,
Thanks for your help. 505F and 806R primers. Here's my code from the denoising:
qiime dada2 denoise-paired
--i-demultiplexed-seqs tai-demux.qza
--p-trim-left-f 5
--p-trim-left-r 5
--p-trunc-len-f 247
--p-trunc-len-r 231
--o-table table.qza
--o-representative-sequences rep-seqs.qza
--o-denoising-stats denoising-stats.qza
qiime feature-table summarize
--i-table table.qza
--o-visualization table.qzv
--m-sample-metadata-file tai.mapping.txt