Not to be blunt but you really should buy one. You will need one on a very frequent basis. If you need to borrow one every time u want to change water your husbandry will suffer.
If money is an issue get a swing arm and calibrate it with someone's calibrated refractometer...while swing arms aren't super accurate, they are consistent
Torqued;1087274 wrote: Not to be blunt but you really should buy one. You will need one on a very frequent basis. If you need to borrow one every time u want to change water your husbandry will suffer.