[SG Sam]

Manage to get some decent pictures

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[SG Sam]

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[odin]

I'm not sure what they are, You are doing correct to remove them until we can identify them because you don't want your Opae ula to be killed if they are indeed predators. I will do some searching online for you.

[SG Sam]

Thank you. I manage to vacuum out around 20 of it. But I think there are still some more in the tank

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[SG Sam]

So for the time being I keep my Opae Ula in a separate container

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[Opaeforms]

I breed Hyalella azteca as fish food and they look like these. They also live in my fish tank and as long as they have predators (I have a dwarf puffer) in the tank with them their numbers stay under control. If they don't have predators and a food source/live plants in the tank they will explode in numbers. They make quick work of plants and mosses.

I introduced a few to my Opae Ula tank (before I put Opae Ula in) in the the beginning but regretted it quite quickly. I removed the HA after a few days of introducing my Opae Ula fearing that they may eat them!

If they are a similar organism to what I have they will survive the biggest nitrate spikes, 2 degree temperatures and are pretty much invincible!

[opae ula related]

Opaeforms, how are your dwarf puffers? I always wanted the keep them.

[SG Sam]

Hi Opaeforms, so is it possible to remove all of them from my tank?

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[Halocaridina]

I agree with Opaeforms, they look like amphipods of some sort. Even though Hyalella azteca can live in brackish conditions, I do not think they are Hyalella azteca specifically because of how long the front antennae and arms are and because they came with chaetomorpha, suggesting they are probably marine amphipods. A lot of marine aquarists grow chaeto in 'refugiums', a type of planted tank connected to the main display tank. These serve two main purposes: nutrient export and a sanctuary for zooplankton (amphipods, copepods, ostracods, mysis shrimp) that make their way into the main tank over time, providing fish with a natural source of food. Sometimes seahorses are kept in these refugiums, as they will only feed on live food and enjoy a more macroalgae-heavy environment rather than a traditional coral reef. If these are marine amphipods, you may be able to kill them off by reducing the SG.

Nevertheless, the behaviour of marine amphipods will probably be similar to H. azteca. I know H. azteca hunts smaller freshwater crustaceans, they maul and devour Daphnia. Most amphipods will eat anything - plant matter, animal matter, dead or alive, even each other. I definitely think you made the right choice by keeping them away from the opae ula!