HDPE is widely considered a very safe form of plastic, with low risks of leaching or off-gassing. HDPE is approved by the FDA and NSF as BPA free, and safe for use with products that will be used with or around humans. You can find HDPE all over the place in the average home, including grocery bags and milk jugs.
HDPE is considered a "low-hazard plastic" and is safe for both use with fish, and products for human consumption.