80cm

I’m a newbie who was gifted a small Fluval Spec 19L tank (″ (W 52 x D 19 x H 30 cm, for reference) with 5 armano shrimp and a few fish (not sure what they are!) about 4-5 months ago. I have some tap safe and water cleaner, and have been doing 10-15% water changes every 7-14 days. I'm in London...