Thank you Fishboy for response on my post. I got little update about my dosing system. month ago I was able to purchase this piece of equipment on eBay- Labconco multistaltic pump (model# 426-2000). I am very happy with the result. Mine set up is working with without any problem. I had a couple issue with purchase supplies for this pump. Unfortunately company who make this pump no longer provide replacement parts. I went to local hobby shop and I was able to find tubing and belt suitable for this setup, together whit electric timer I was able to control amount of dosage of chemicals for my saltwater aquarium. You can control up to four different chemicals(same speed of dosing). After testing in slowest speed it takes about 29 minutes for 10 ML of solution be distributed. you can also add purified water to your chemicals for greater control of distribution. Electric timer can be set up for many short cycles. By small dosage of chemicals (calcium ect.) stress on tank can be greatly reduce. I just hope that the information is going to help some of you guys.
And finally response to the gentleman above I recommended Home Depot. They have good supply of black paint.