[galaxy-user] how to split paired-end dataset of FASTQ format

I downloaded RNA-seq dataset at FASTQ format from SRA of NCBI. I uploaded the dataset onto Galaxy. The dataset is paired-end. I want to split it into two datasets (one for each end) with FASTQ splitter. But the name of the dataset does not appear under "FASTQ reads". How should I do to solve this problem? Thanks. Jianguang