[odin]

Welcome to the forum! I'm going to split up your questions to best answer them :)

A 2litre lab flask will be fine so long as you do remove the lid often enough to let fresh oxygen into the container, how much air can get stored between the waters surface and the bottom of the lid? The tank needs a good pocket of oxygen to remain healthy.

Starting out with 10 Opae ula is good number and you should have at least one female in there, it's difficult to distinguish the males and females apart by eye so you will never know until they carry eggs. Linking this question to the next if you are concerned about breeding then I would suggest getting something to check the salinity of your water.

You can buy a floating hydrometer if you cannot buy a normal hydrometer or refractometer, they are very cheap and look just like a floating thermometer. It floats in the water and sits higher or lower depending on the salinity of your water.

See below:
Marble substrate is fine but what do you mean cycled it with ammonia? Is your substrate in the tank already with salt water because you are cycling the full tank?

What type of ammonia have you used? You need to use the fragrance free stuff to cycle a tank and did you use a water test kit to see if it had cycled?

I will be honest and suggest you setup your tank this way;

- Rinse the container with RO water, and rinse the marble substrate the same to make sure you remove all the ammonia.
- Add the substrate to the tank and fill the tank up with RO water, weigh out enough salt to match half of what the packet suggests as they suggest the quantity to use will produce full on marine salt water while you want half salt brackish water.
- Add your rocks and calcium carbonate source.
- Switch the lights on for at least 12 hours a day and wait for the tank to start growing algae.
- Once you get lots of green algae on the glass (this comes after the brown algae) you can add your shrimp.

I hope this helps and answers your questions, any issues then ask away :)

[odin]

No worries

How did you cycle the marble? i mean the process? With regards the marble buffering your water (which is what you use calcium carbonate for) this is a bit of a difficult one, Marble is in its own right a metamorphic stone made up mostly of crystallized calcium carbonate (limestone) See: Wikipedia but this dosent mean it will work to do what we need it to do. The best way to test this is to get a piece of the rock and pour some vinegar onto it, if it hisses or bubbles then the rock will affect the tank PH which you do want and you wont have to worry any further or buy anything extra to buffer the PH. If it doesn't then you will have to buy something that will keep the tank waters PH nice and high.

I'm glad you mentioned about the need for an air gap and the answer is a yes, you will need a big air gap or a lid that is not air tight, although algae releases oxygen it will need to go somewhere and that is out of the tank water into the 'air gap' This helps with gas exchange too when it breaks the surface. Those sealed globes stop/prevent any clean oxygen getting into the tank and don't provide a healthy environment for the shrimp, this will shorten the length of their life plus you will not get any breeding if the water isn't perfect for them

The food source for the algae being skin is a very interesting theory but the truth is the bio-load from the shrimp and snail waste plus dying plant matter is one of the sources of food (indirectly of course) feeding the algae, which in turn feeds the shrimp.

If you setup your tank like i suggested you will definitely be onto a winner and have happy healthy shrimps

[odin]

Ok thats the best way to cycle somthing Do you have any photos of your flask you wish to use?

[odin]

That looks great! i like the idea, have you seen the bungs/plugs that have holes in them? they are for having pipes running though like this:

cGM0BAn.jpg (2.89 KiB) Viewed 11909 times

https://www.google.co.uk/search?q=Erlen ... 981#imgrc=_

You could experiment with a tiny bit of hose that just folds over and that would stop any cleaning agents falling in.

[odin]

Sort of like this but don't have the pipe going into the water and cut the pipe on the outside of the stopper/bung just enough to have it bend over so it is facing downwards.

Cut where the Red lines are:

STFaIS3.jpg (191.54 KiB) Viewed 12326 times

[odin]

The algae will indeed produce the oxygen they need but you will still need to have a space between the stopper/bung and the waters surface, if you have a glass stopper that is indeed sealed you would need to have an inch or so gap for air between the water and the lid/stopper and remove the stopper and place it back once a week, you should be good to go and it would like a lot nicer

[odin]

It really just comes down to oxygen being let in, its just good practice and although these shrimp can survive in low oxygen levels we have no way of knowing if the small bubble of air in your sealed container is enough to keep the living creatures healthy, Its not worth the risk!

Here is an extract that should help explain:

"Gas exchange - where the water dissolves oxygen and other gases from the air and releases excess carbon dioxide and other gases to the air - occurs over any and all surface area where the water has contact with air. By increasing the surface area of the water, each bubble gives the water further opportunity to release carbon dioxide and take up oxygen."

Shorthand: You don't want a build up of anything but oxygen in the top of your sealed tank as less oxygen can be stored. You are going to remove the lid once a week or so, so none of this will apply and you wont have anything to worry about.

With regards the instant ocean, just half the amount. You can always use half the amount of water they suggest and a quarter of the salt you are told to use, failing that just whip up a full bucket by the instructions, use half the salt and just use what you need a pour the rest away.

[odin]

Either way if it doesn't take then it will rot and die and produce ammonia, that will turn into nitrites and feed nitrates which will feed your algae when it starts to grow.

[odin]

Thats a great tip with the substrate, luckily i didnt run into that issue.

[odin]

I would use the 2000ml personally, what makes you think its too big? I think you may struggle to keep a good water health balance with 500ml, can you not buy a 1000ml one?