# \#18s **URL:** https://forum.qiime2.org/tag/18s/208.md [Latest](https://forum.qiime2.org/latest.md) · [Categories](https://forum.qiime2.org/categories.md) · [Tags](https://forum.qiime2.org/tags.md) --- ## [Why are my reads filtered out (98%) when quality seems okay?](https://forum.qiime2.org/t/why-are-my-reads-filtered-out-98-when-quality-seems-okay/34292)
**Author:** [@lineroager](https://forum.qiime2.org/u/lineroager)\ **Replies:** 6\ **Last updated:** [August 20, 2026, 11:38am UTC](https://forum.qiime2.org/t/why-are-my-reads-filtered-out-98-when-quality-seems-okay/34292 "2026-08-20T11:38:51Z")
I am using qiime2 2026.7 on a WSL system in Ubuntu and working on paired-end 18S seq data (Illumina Miseq 2x300) from a mixed seawater community. My data is already imported and demultiplexed, but at the denoising step (… --- ## [ITS, 18S, 23S and 28S new reference databases to use in QIIME2](https://forum.qiime2.org/t/its-18s-23s-and-28s-new-reference-databases-to-use-in-qiime2/33018)
**Author:** [@A\_Munoz](https://forum.qiime2.org/u/A_Munoz)\ **Replies:** 0\ **Last updated:** [April 17, 2025, 1:37pm UTC](https://forum.qiime2.org/t/its-18s-23s-and-28s-new-reference-databases-to-use-in-qiime2/33018 "2025-04-17T13:37:07Z")
MIMt database has grown and now it includes databases for other markers like ITS, 18S, 23S and 28S to the previous 16S already in use. All the databases have two versions, one with only curated sequences from Target Loc… --- ## [SILVA vs PR2 database using qiime2](https://forum.qiime2.org/t/silva-vs-pr2-database-using-qiime2/32787)
**Author:** [@Adyasha\_Panda](https://forum.qiime2.org/u/Adyasha_Panda)\ **Replies:** 1\ **Last updated:** [March 19, 2025, 1:33pm UTC](https://forum.qiime2.org/t/silva-vs-pr2-database-using-qiime2/32787 "2025-03-19T13:33:55Z")
Hello everyone, I Have some 18S amplicon sequenced data from marine. I Have ran DADA2 For denoising after that I have done taxonomy classification using both silva-138-99-nb-classifier.qza and pr2-classifier.qza. It gav… --- ## [DADA2 error for 18S paired end reads](https://forum.qiime2.org/t/dada2-error-for-18s-paired-end-reads/31992)
**Author:** [@nietof](https://forum.qiime2.org/u/nietof)\ **Replies:** 3\ **Last updated:** [November 27, 2024, 1:44pm UTC](https://forum.qiime2.org/t/dada2-error-for-18s-paired-end-reads/31992 "2024-11-27T13:44:08Z")
Hi I have a similar problem. I am denoising 11 samples paired end reads for 18S amplicon. I am running the qiime2-amplicon-2024.5 installed natively in my macbook pro 2.3. GHz 8 core intel core i9 with 64GB RAM and 1TB … --- ## [merging sequence runs with slight primer variation](https://forum.qiime2.org/t/merging-sequence-runs-with-slight-primer-variation/27142)
**Author:** [@spongebob](https://forum.qiime2.org/u/spongebob)\ **Replies:** 8\ **Last updated:** [August 15, 2023, 2:32pm UTC](https://forum.qiime2.org/t/merging-sequence-runs-with-slight-primer-variation/27142 "2023-08-15T14:32:39Z")
Hi all, initial analysis done with qiime version: qiime2-2019.10 I have two data sets of 18S rRNA gene sequences from different sequence providers. The only difference is the reverse primer has an extra trailing TGA D… --- ## [Regarding Databases](https://forum.qiime2.org/t/regarding-databases/27285)
**Author:** [@Jaykishan\_Solanki](https://forum.qiime2.org/u/Jaykishan_Solanki)\ **Replies:** 3\ **Last updated:** [August 3, 2023, 5:32pm UTC](https://forum.qiime2.org/t/regarding-databases/27285 "2023-08-03T17:32:15Z")
can anyone guide me from where i can get pre-formatted databases for ready to run 18s rRNA data analysis ?? --- ## [18s merge problems after using cutadapt](https://forum.qiime2.org/t/18s-merge-problems-after-using-cutadapt/25652)
**Author:** [@hankpp](https://forum.qiime2.org/u/hankpp)\ **Replies:** 7\ **Last updated:** [April 11, 2023, 6:25pm UTC](https://forum.qiime2.org/t/18s-merge-problems-after-using-cutadapt/25652 "2023-04-11T18:25:51Z")
Hello, I am working on amplicon sequencing data of some markers, including 18s (with 1391F and EukBrR primers), using qiime2-2022.8. One of the problem I found is readthrough, in which target lengths are less than the r… --- ## [Can 18S rRNA full length sequencing data detect archaeal diversity..?](https://forum.qiime2.org/t/can-18s-rrna-full-length-sequencing-data-detect-archaeal-diversity/24467)
**Author:** [@Duminda](https://forum.qiime2.org/u/Duminda)\ **Replies:** 0\ **Last updated:** [October 17, 2022, 4:34pm UTC](https://forum.qiime2.org/t/can-18s-rrna-full-length-sequencing-data-detect-archaeal-diversity/24467 "2022-10-17T16:34:34Z")
Can 18S rRNA full-length sequencing data detect archaeal diversity..? --- ## [Error with the command I used for deblur other](https://forum.qiime2.org/t/error-with-the-command-i-used-for-deblur-other/15985)
**Author:** [@Mandy](https://forum.qiime2.org/u/Mandy)\ **Replies:** 10\ **Last updated:** [August 7, 2020, 4:46pm UTC](https://forum.qiime2.org/t/error-with-the-command-i-used-for-deblur-other/15985 "2020-08-07T16:46:56Z")
Hello, I wanted to use Deblur other for 18S so I could compare the results to DADA2, I'm having a hard time getting the command right, and I always receive the same error. This is the command I used: qiime deblur denoi… --- ## [Trying to understand \`ids\_to\_keep\` must contain at least one ID. error](https://forum.qiime2.org/t/trying-to-understand-ids-to-keep-must-contain-at-least-one-id-error/14116)
**Author:** [@kevin\_dillon](https://forum.qiime2.org/u/kevin_dillon)\ **Replies:** 2\ **Last updated:** [March 19, 2020, 10:46pm UTC](https://forum.qiime2.org/t/trying-to-understand-ids-to-keep-must-contain-at-least-one-id-error/14116 "2020-03-19T22:46:10Z")
Hello, first off, I’m brand new to QIIME and amplicon analysis. I’m having an error come up when importing pre-processed fastq files into QIIME and then making a feature table. I have partial 18S rRNA gene sequences gen…