You don't need a degree in Chemistry to make your own aquarium chemicals. It would help - and never pass up the chance to learn more chemistry, ever, but high school science is all you need to know... the idea is, if you can follow a recipe to make cookies, then you can also follow a recipe to make your own aquarium fertilizer, de-chlor and most of the things here. It's easy and extremely economical, plus you know exactly what your dealing with and are in man ycases safer. For example, look at what we use here to get rid of chlorine and chloramine and compare then ti stuff you buy that until fairly recently had formaldehyde in it.
Seawater might be a bit of a challenge for a novice as the trace elements are in tiny amounts but this is not even remotely impossible for even a novice to do. Much simpler are the aquarium fertilizers, they truly are as easy to make as cup of tea... except you don't need to boil water.
Some good some bad. I had a little to do with the popularization of the use of bleach and peroxide because of articles I wrote about them in TFH. I wish I never had. Those things are nothing but trouble.
One gram of ascorbic acid will neutralize 1 milligram per liter of chlorine per 100 gallons of water. The reaction is very fast. The chemical reaction (Tikkanen and others 2001) of ascorbic acid with chlorine is shown below:
Approximately 2.5 parts of ascorbic acid are required for neutralizing 1 part chlorine. Since ascorbic acid is weakly acidic, the pH of the treated water may decrease slightly in low alkaline waters. - Dustin Carver
See also:
Using Vitamin C To Neutralize Chlorine in Water Systems
The intended audience is sanitary engineers and operators of water and wastewater systems.
Brenda Land, Sanitary Engineer, Project Leader https://www.fs.fed.us/t-d/pubs/html/05231301/05231301.html
"Under aerobic conditions, microbial activity can degrade cyanide to ammonia, which then oxidizes to nitrate. This process has been shown effective with cyanide concentrations of up to 200 parts per million. Although biodegradation also occurs under anaerobic conditions, cyanide concentrations greater than 2 parts per million are toxic to these microorganisms."
"Algae and macrophytes can tolerate much higher environmental concentrations of free cyanide than fish and invertebrates, and do not exhibit adverse effects until 160 micrograms per liter or more. Aquatic plants are unaffected by cyanide at concentrations that are lethal to most species of freshwater fish and invertebrates."
Over a period of about 20 years or so, mostly on the net, liquid aquarium fertilizer changed from either mostly useless and spooky things to complete and well understood regimen of the optimum nutrients. The formulas are dead simple and the ingredients can be bought in any decent drug store or grocery store and hardware store.
Creemore Ontario has the hardest water I've seen in the world - 1200 ppm carbonate hardness in the water. Fill an aquarium with it and by morning fine layer of chalk dust will have settled out on the bottom.
Life exists in pure rainwater pools, and species that have adapted to this are a special challenge in the aquaria.
Hobby test kits are not accurate, and nitrates may not be as harmful as people believe.
My nitrate test bottles were down to probably a few tests left so I ordered a new Kit and compared the result out of curiosity. New: 10-20 ppm, Old: 40-80 ppm. I only had the old kit for about a year."
