Sensors vs test kits recommendations

[D3vilR4y]

Hey everyone, I’m both new to the site and the hobby and I could really use some advice. I’m a graduate student starting a project studying tropical fishes and I’ve been running into some road blocks with my tanks. I’ve read a couple threads here with similar questions, but since I’m trying to set up and maintain ~10 small volume tanks (x2 10gal, x8 20gal), I’m not sure how relevant the recs on other threads are.

I’m trying to figure out the best ways to test for salinity, pH, and nitrites/nitrates. The rest of my lab is on a seawater flow-through system that connects to the ocean, but the water is too cold for my tanks so I have to have closed systems. Because of that, I’m trying to figure out what test kits are the best for my nano FOWLR tanks or if I should invest in some sensors.

For people with a bunch of tanks, how do you measure all of your water parameters? Do you prefer sensors or test kits? I’m interested in how much easier it would be to use sensors to get consistent readings quickly without creating a bunch of waste, like used strips and water with chemicals. That being said, I want to prioritize accuracy and I’m limited by a somewhat tight budget.

Here’s what I’m currently using, I’d appreciate any advice, suggestions, or feedback!

Salinity: Coralife Deep Six Hydrometer

- We had a handheld refractometer that you look through, but it seemed to lose calibration everytime it moved. Learned that the hard way after it misread a tank as 1.023 as 1.035.​

Ammonia: API Ammonia NH3/NH4 test kit

pH: Test strips 5 in 1 (pH, NO2, NO3, KH, GH)
- Colors are not my strong suit. I don’t know if I’m a little colorblind or if the color cards in these kits are a little off, but I’m never sure how accurate my interpretation of the ammonia and pH readings are.

Thank you all so much!

Edit: some grammar fixes

 

[Randy Holmes-Farley Verified Community Expert]

I recommend pH and salinity by sensor. Both sensors can easily be moved tank to tank so you do not need 10 of them./

Not sure you need to measure nitrite unless you are doing something to generate it or you have a driving interest in quantifying low levels. It's not a tox issue in marine systems.

 

[D3vilR4y]

I recommend pH and salinity by sensor. Both sensors can easily be moved tank to tank so you do not need 10 of them./

Not sure you need to measure nitrite unless you are doing something to generate it or you have a driving interest in quantifying low levels. It's not a tox issue in marine systems.

Thank you! Do you have any suggestions for specific brands or models I should look into?

 

[Randy Holmes-Farley Verified Community Expert]

Not particularly. The ones I use are typically lab devices sold used.

For a pH meter, I think a separate probe and base unit are better, but cost more than pen types.

As to conductivity for salinity, many folks do not like the Hanna pen type. You might avoid that one.

Folks also like the Tropic Marin large floating glass hydrometer for salinity.

 

[Privateye]

Unfortunately the only sensors I know of that measure ammonia or nitrate only work in freshwater.

A lot of this depends on your budget. At work I use a YSI multiparameter meter to measure a few things, including salinity and pH. They're kind of pricey though (a few thousand dollars). A good hydrometer or refractometer is fine for salinity, and you can buy pH sensors for pretty cheap.

For nitrate, I'd probably go for a Hanna Checker. The low range goes from 0-5 ppm and the high range goes from 0-75 ppm. The high range model is less-accurate at low nitrate values. With both strips and the API kit, it can be difficult to determine the concentration at the low and high end of the ranges. The differences in color tend to be easier to read towards the middle of the range. Be sure to avoid any instruments that use the cadmium reduction method (inaccurate in saltwater).

Randy has a good point about nitrite. Unless you plan to create some weird conditions it will likely be very low, stable, and not harmful. If you plan to maintain elevated nitrite values then you would want to measure them though. When you're using devices that measure "nitrate" by converting it to nitrite and measuring that (e.g. Hanna Checker) you'd need to subtract the nitrite concentration from the nitrate to get the true value.

Ammonia may not need to be measured either, depending on the study. I'll leave that up to you. It may be one of those parameters you don't measure as often, but just often enough to write "ammonia levels were maintained below _____..." in the paper.

If that's the level of information needed, then the API kits are probably fine. IME they're accurate, but imprecise. If you need more precision then perhaps you'd want to look into some sort of photometer/colorimeter (e.g. LaMotte Smart Colorimeter, YSI 9800 photometer, etc.) but you'd be spending a lot more than you would on liquid test kits.