While the topic of compressing FASTQ comes up, you might be interested to know that kmer sorting FASTQ files can lead to around an 8% improvement in compression

While the topic of compressing FASTQ comes up, you might be interested to know that kmer sorting FASTQ files can lead to around an 8% improvement in compression depending on the diversity. I believe this is because it puts similar strings together in the tree gzip uses. clumpify.sh from bbtools is one example.