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Shrimplet survival issues


Rosstifer
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Hello and thank you in advance for any input. I'm having an issue with shrimplet (neocaridina) survival in my tank. Colony was originally started in a 40 breeder and when the population begin getting close to maxed out, was moved into a 180. The population grew pretty quickly for the first 3-4 months (currently been in new tank for around 10 months now), but then growth slowed way down and hasnt increased too significantly since then.

Some info on the setup. 180 gallon tank orignally started with three large sponge filters, but a couple months ago installed a custom canister/uv sterilizer using one of the sponge filters, slightly modified, as the intake to prevent any shrimplets from being sucked into it. Substrate is a shallow layer of black diamond sand blasting sand from tractor supply. Had a lot of plants in the original 40 breeder the colony was in, but switched over to only moss when moved to the 180 for ease of mainenance. Introduced as tissue cultures originally, so there wasnt a lot at first, but since then its grown into a pretty significant amount. The water used is RO remineralized with saltyshrimp gh/kh+. Perameters are usually right around 200 tds, 7gh, 2-3 kh, 7.5 pH, 20-40 nitrate. Water changes of 20-25% bi weekly. Fed daily with a mix of blanched zucchini/cucumber, glasgarten shrimp dinner/shrimp baby, snowflake pellets, bacter ae. Also have driftwood and a variety of leaf litter for biofilm growth. 

Around the fourth month after being moved into the bigger tank, the shrimplets pretty much completely disappeared. Found that there was small amounts of chloramine still left in the RO water and after that was fixed, shrimplets began to appear again. There was a bit of growth again in the colony, but before long it seemed to have pretty much stopped for the most part. There are shrimplets around, but nowhere near the amount I would expect for how many berried famales there are. The population doesnt really seem to be in decline, I dont see many dead shrimp, but there just seems to be very little change in the population for months now. I have quite a few theories as to what the problem might be, and suspect it might be a combination of different things that might be stalling the growth, and am hoping to get some input on what the most likely culprit is, or any suggestions for things to try. 

One of my biggest suspects is that there are a LOT of copepods in the tank. They were in the original 40 breeder the colony was started in, and despite efforts to not bring them over to the new tank, they came anyways. It took a while for their population to grow to worrying amounts, but its now definately a worrisome amount. Part of the reason we began using the canister/UV sterilizer was to hopefully put a dent in their population, and after messing around with some different types of sponges for the canister intake, I've found one that is porous enough to mostly prevent shrimplets from being sucked in, but is able to suck in the smaller copepods. The copepod population has definately declined, but this is a recent change so the results are still up in the air. Do you think a plaguelike amount of them would be able to strip the tank of enough biofilm to bring shrimplet growth to a halt?

Another thing i have suspected might be causing the low shrimplet survival rate is water quality issues. Mostly high nutrients is what ive suspected, but also possibly too many/too large waterchanges. In the original 40 breeder, the amount of plants eventually reached the point where nitrates were always very close to 0 and I was able to do a very minimal amount of waterchanges. It seemed like it was around that point that the shrimp really began to thrive and population density increased quite a bit. Now in the 180, the amount of moss is finally reaching the point where it is actually able to have somewhat of an impact on nutrient levels and nitrates have been staying around the 20-30ish range, but up until now it was usually more like 40-50. Because of this, i was doing pretty large waterchanges regularly. The amount and regularity of which has varied from time to time as Ive tried different things to get this sorted out, but at certain points it was up to 35% every 10 days or so. To prevent drastic changes in water chemistry, the water is always mixed using the same remineralizer, to the same tds, and the tank is filled back up slowly using a float valve over the course of 5 hours or so. would you think either the high nitrates or large waterchanges would be able to cause low shrimplet survival?

When I first began to notice a lack of shrimplets, the first thing I assumed was that there wasnt enough food/biofilm for them, so I began experimenting with varying amounts and types of food. Tried increasing the amount of pellets fed, keeping blanched veggies in there regularly, and feeding more powdered food. This didnt really seem to have much of an effect on the amount of shrimplets and the copepod problem seemed to get worse, so ive since cut back quite a bit on the amount fed, but am still feeding daily. It was around that time that the amount of  moss in the tank began to really take off too and much of the substrate is now completly covered in moss. When doing maintenance, i began to notice that there was a lot of detritus accumulating under the moss. I wouldnt normally be too concerned about it in a normal fish tank, but the amount seems to be getting larger and have considered that a large amount of it, possible also mixed with uneaten food, could be getting trapped under the moss and impacting water quality. It doesnt seem to be bothering the adult shrimp, but is this something that could have more of an impact on shrimplets? They definately seemed to do much better when the tank was newly set up so it makes me wonder if accumulating waste could be at least part of the issue.  It wouldnt be easy to do with shrimp everywhere, but should i get in there and try to get as much of the detritus siphoned out as i can?

One thing I suspected a while back, but have since mostly disregarded, is a lack of good hiding places for newborn shrimp. Ive added some rock piles and the moss has grown in quite a bit since then so ive kind of stopped worrying about it, but as I said maybe its not one main issue and several smaller ones all contributing. Should I try to give the newborn shrimplets more small nooks and crannys where they can hide away from the hustle and bustle of the adults? I'm trying to be as patient as I can, as I know most of these changes probably arent going to fix things overnight, but I'm starting to run out of ideas on what to do in order to get the shrimplet survival rate up and increase the overtall population density. Any suggestions would be greaty appreciated, even if its not a solution but just what likely ISNT the problem. Thank you in advance and let me know if you have any questions about the setup or maintenance routine.

 

 

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4 hours ago, Rosstifer said:

Do you think a plaguelike amount of them would be able to strip the tank of enough biofilm to bring shrimplet growth to a halt?

Copepods themselves don't pose much of a threat to shrimps. Apart from out competing the shrimp for food. They would be eating the same foods as adult and baby shrimps. 

Copepods can be unsightly in a tank, especially in plague proportions. Unfortunately anything that will kill them will also kill shrimps. The only method that I have had success with is to catch all the shrimp and start a new tank. Do not reuse the gravel, plants or filters. Nothing from the old tank must move to the new tank. The shrimps are caught and placed in a temporary tank/hospital tank, for a few days while the new tank is set up, and then caught again to be placed in a new tank. 

It's pain for sure.

Oh, another method that works is to add fish! As long as the fish are shrimp friendly of course. 

4 hours ago, Rosstifer said:

To prevent drastic changes in water chemistry, the water is always mixed using the same remineralizer, to the same tds, and the tank is filled back up slowly using a float valve over the course of 5 hours or so. would you think either the high nitrates or large waterchanges would be able to cause low shrimplet survival?

High Nitrates can be an issue for shrimps and shrimplets. So I would put this high on the list to remedy. High Nitrates is linked to detritus. See below.

4 hours ago, Rosstifer said:

It wouldnt be easy to do with shrimp everywhere, but should i get in there and try to get as much of the detritus siphoned out as i can?

 Heavy amounts of detritus is one of the causes of Nitrates. Detritus that has sunk deep into the gravel, and stuck on filter media can be the causes of Nitrates increasing. When was the last time you gravel vac'd? Or the last time you squeezed out your filter sponges and cleaned the filter media? Of course, cleaning media should be done in the old tank water. Never clean filter media in chlorinated tap water.

Lots of fast growing plants also help control Nitrates. 

Do you still have the old 40 tank? I would use that as a temp holding tank and move all your shrimp across while working on the 180 tank. 

5 hours ago, Rosstifer said:

black diamond sand blasting sand

Sand, even if it's black blasting sand, can get compacted and trap detritus. I would look at replacing it with substrate that has a similar shape to ADA Amazonia. That round shape has a reason. It allows more water flow between and as a result is "lighter" and easier to clean with a gravel vac. Plant substrates also have other benefits like holding more nutrients for plants, easier to plant with and has pH buffering abilities. 

Yes, that is an increase in costs, but I have never thrown out old ADA substrate. I use it new in my Caridina tanks. And when the substrate has lost it's nutrients and buffering capabilities, I wash and re-use it in my Neocaridina tanks. 

 

Hopefully this has given you some ideas. 

 

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The copepods are only really a problem as they compete with the shrimp for food, and look unsightly, but are actually otherwise a good thing and indicate the tank is good! As mentioned by JayC, I had success using fish, they wiped out the infestation in a couple of days.

Every environment will find its 'maximum occcupancy' level based on how many it can sustain, and this can be increased with additional food but thats a difficult balancing act to get right.

If the filter is clearing some of the copepods, then it will almost certainly also be clearing some of the new born shrimp (hense the decline) as they are similar sizes, rarely do you see newly born shrimp as they are soooo small.

I would do as JayC recommends and change the substrate, but would also add some nano fish and plants as it is quite a big tank? Most substrates have some sort of run-in period so this may mean putting the shrimps back in the old tank for now?

Shrimp don't need hiding places, unless there is something that predates on them. If you want to try the fish route then sufficient plants/cover/hideouts would be recommended to maximise the survival rates of the shrimps. If you do use soil substrate with plants you don't need additional plant fertilizer as the soil and shrimp waste will cover that.

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