HCA: Hermit Crab Association

Sorry if the is has been discussed but I couldn’t find it if it has.

I can’t keep nitrate levels lower than 5 ppm. My tap water has about 5 ppm as well. Maybe slightly lower but not 0.

If I use prime it will lower it but only for 48 hrs.

I tried plants in the freshwater which will lower nitrates but I think my lighting isn’t strong enough.

As for the saltwater i don’t know what to do. Water changes with prime treated water doesn’t seem to lower nitrates that much.

For now I just put a couple drops of prime in each pool.

The reason I know prime lowered my nitrate levels is because I tested the water and added one drop of prime to the test tubes. After that the color changed so I know it works but that’s a much higher concentration of prime than two drops per gallon.

Like I said I added 2 drops in each 1 gallon pool but walked away. I’m not sure how much that lowered the nitrates but I’ll test my pools again tomorrow.

I know 5ppm isn’t much but for inverts I don’t know.

Can anyone help me out here? Should I start using a different source of water? I’m not wanting to dose prime every other day into the pools.

5ppm is fine, for saltwater most try to keep it under 20ppm and for freshwater, most try to max it out around 20-40ppm. You'll find as both pools mature, nitrate removal will increase as bacterial colonies develop.


For freshwater, floating plants or semi submerged plants (lile pothos, arrowhead vine, aluminium plant ect... roots grow in water) do the best for nitrate removal as they aren't limited by CO2 levels in the water.

Long story short, no need to dose prime daily as nitrates isn't as toxic compared to ammonia and nitrite.

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Awesome! Thanks.

I have been wondering if it was ok to add pothos to the freshwater because I can stretch it towards the light but I didn’t know if it might release something into the water since it can be toxic if the crabs eat it. I had it in the tank before with no problems but I didn’t have the roots in the water. Ive also kept a betta with pothos for years.

I did have duckweed before but it either died or got eaten. I didn’t have much in there so who knows. I thought it would do fine in low light as I’ve seen it cover a pond that was in the middle of a forested area.

I’ll try the pothos roots in the freshwater!