Shrimp dying/dissapearing

[JakeSpell]

Heloo all!

I have a 20G planted tank that has been cycled for about two months. It currently has 6 Serpae tetras, 4 Nerite snails and a handful of ghost shrimp and 3 RCS.

It seams that anytime I get shrimp one or two of them go missing after the first day but untill a few days ago I never found a dead one then all of a sudden I saw two covered in fungus and promptly removed them. This morning I found another dead RCS stuck to the filter intake.

All my parameters are normal.
Amonia 0
Nitrite 0
Nitrate ~30ppm
pH 7.6
GH 8
KH 2
Temp 75F

I do 20%PWC every week.

Any idea whats going on? All the fish/snails seem to be very healthy.

 

[Fishfur]

I see two problems. Your KH is very low, thus there is not much calcium in the water, which is essential for normal moulting and shell growth. Cherry and Ghost shrimp need hard, alkaline water with plenty of calcium in it.

And your tank is just not old enough to support shrimp. They need a good supply of biofilm, which takes at least four to six months to grow once the tank is cycled. They eat it, for one thing, but there is something else about it too, which is not well understood., some kind of relationship between many fish and inverts and biofilm. Many fish species don't do well in new tanks and shrimp certainly don't do well in them.

I'd get that KH up, some crushed coral in the filter, small amounts to start with, test, add more if needed, 'til you get a good level of calcium. And wait for some biofilm to grow before you try again.

Without enough calcium in their water, newly moulted shrimp may not have enough of it to harden the new shell, leaving them soft and very vulnerable. It will affect the snails too, but because their shells are thicker and harder, calcium deficiency may not show up as soon in them.

 

[aluka]

Your kh is fine, the other poster is mixing gh and its relationship with calcium. Most likely your fish is eating/killing the shrimps.

 

[Fishfur]

I will never claim to be an expert on water chemistry, but my understanding of KH is that 2 to 3 german degrees is the minimum necessary simply to prevent pH swings. The shrimp need more than that to maintain their shells and moult properly.

GH is calcium and magnesium together, what we call the hardness of water, while KH is more about buffering capacity, calcium carbonate and bicarbonate.

If I have this wrong, do please explain it, I like to learn.

Edit. Serpae tetras are not large enough to eat a Ghost shrimp or a full grown cherry shrimp. Baby shrimp, sure, they will eat those.

 

[JakeSpell]

I'v only lost one cheery shrimp. They seam to be out and scavenging a lot more over the past few days. I want to get the kh/gh up a little but as is my pH is slightly higher than I want. Would a little crushed coral still be a good idea?

 

[Fishfur]

The shrimp can handle pH up to 8.. so if it raises it a point or two, should not be a problem for the shrimp.

But the tetras won't like it that high for sure. They prefer it much lower than that, neutral or slightly acidic, which is not so good for the shrimp, something I should have realized sooner.

Not really the best combo of fish and inverts to have in the same tank, but I have seen tetras and cherries in the same tank and apparently both ok.

Even one point of pH is a fairly dramatic change, 10x more or less than the level below or above it. I am not sure at this point what would be the best to do. Simply waiting for awhile before you get more shrimp may serve you better.

 

[JakeSpell]

I think I'll just let the tank be for a while, continue with my water changes and keep ya posted!

Thanks for the advice

 

[aluka]

One of my friends got 5 neo tetras to put his cherries, his colony went from 30+ to less than 10 in 2 weeks. Op's tetras can grow up to 2 inches, while they are not big enough to eat an adult shrimp whole, they certainly are big enough to kill them or stress them to death. Unless there is alot of hiding places for the shrimps, many shrimp + fish combos will fail.

Most shrimp breeders actually keep KH at 0 for shrimps (except for tiger shrimps). Because they are more motivated to breed at low kh. In nature, they breed during the rainy season, when kh is pretty much 0. So while higher kh might not kill them, but will cause breeding plauses in your colony. So the lack of alkalinity, has nothing to do with the molting of the shrimps. If your shrimp has molting issues, it is due to a GH issues. Kh only measures the carbonate and bicarbonate ions in the water, does not have to be calcium carbonate..

Here is a list of common shrimps and their prefered parameters. Note many of them can live in and prefer lower kh.

http://shrimpkeeping.com/water-params/