short read assembler - Velvet is a de novo genomic assembler specially designed for short read sequencing technologies, such as Solexa. Can be used to do whole genome assemblies of Illumina Genome Analyzer (Solexa) data.

Velvet can use large amounts of memory. Especially if the dataset is not filtered. A good starting point for a 30M fungal genome could be somewhere in the order of 30GB of ram.

To obtain the best possible assemblies, you should do proper filtering of the datasets. Low quality reads and adapters must be removed.