Alternative aquarium test kits

Good Day,

Our group is developing Aquarium system that replaces the use of test kits, basically we would use sensors to check the aquarium instead of using test kits to determine the chemical level.

Our problem is that we researched about nitrite, nitrate, and ammonia and their price is very expensive. But we found out that ammonia can be determined by pH level.

Any advice what sensors can we use instead of this expensive sensors(nitrite, nitrate, and ammonia), but measured by aquarium test kits.

sorry for my bad english, any advice is gladly accepted

As you have found, there are the standard Dip type of test kits, then the immersed but expensive probes.

A few manufacturers have developed a more modern type of water tester, but the price of them and the follow up parts you have to buy are quiet expensive.
Reports of their performance also vary widely.
Here just one of these modern types, others around if you search.
https://www.seneye.com/

If you find a simpler, accurate and cheaper way, then you are on to a winner !

princenpg22:
Our problem is that we researched about nitrite, nitrate, and ammonia and their price is very expensive. But we found out that ammonia can be determined by pH level

No, you can't. You can determine the ratio of ammonia to ammonium from pH, but not the actual level. You must have misunderstood what you read.

There's a good reason why the big companies haven't come out with something like this yet. The sensors are very expensive. And most of those probes can't be used as a constant monitor in seawater. They'll last days or even hours when constantly submerged.