Help Tank nearly cycled now this happens

[Stephen.h]

Been running my cycling fish only Trigon 190 tank for 7 weeks now.
Started with live sand, 20 kg Caribsea Dry Rock, added Fluval Cycle to start the cycle along with frozen shrimp and also nt labs marine filter bacteria.
Canister Filter running only Carbon.

5 weeks in and my parameters were (a little brown Diatom Algae)
PH - 8.0
Ammonia - 1.00
Nitrite - 5.0 ppm
Nitrate - 50 ppm

6 weeks in and looking nearly cycled (Crystal Clear)
PH - 8.3
Ammonia - 0. ppm
Nitrite - 0.25 ppm
Nitrate - 15 ppm

Now
7 weeks in and the Parameters have went back to the same they were at week 5 rather than getting what hoped for Nitrite 0 Ammonia 0.
Also the tank is went from crystal clear to looking cloudy with a green tint.(Using RO)

What would cause this, the only thing have done to the tank is moved some of the sand about the night before more flat. Also had a Canister leak of 10 litres (now fixed) the night before taking to get tested on week 7.

Was all looking like would be complete at week 7 till this happened. What would cause it suddenly to go backwards in water clarity and parameters.
Going to do a 25% water change on wednesday and start my new skimmer see if can get the parameters and water clarity back to what it was.

Many thanks

[julie180]

Part of cycling a tank. Algae bloom. Get that skimmer going, possibly put some type of filter in that canister and wait. Some say not to do a water change on a cycling tank as it could prolong the process. I can't comment on that.

[fermentedhiker]

The cloudy water is just an algae/bacteria bloom and should clear quickly on it's own. If I had to guess I would say your Ammonia/Nitrite spiked because of a die off of the algae/bacteria that had started to consume it. Which then fed your current bloom causing your cloudy water.

Normally I would agree with the idea of not doing a water change during the cycle(just a waste of salt mix usually) but 50PPM of Nitrate is quite high. So I say go for it with the WC and repeat until you get Nitrate down under 10(for now). Also generally there isn't a point in running a skimmer during the cycle(counterproductive really) but at this point I don't think it'll do anything and it'll take a couple weeks to get it dialed in, so you might as well do it now so it'll be performing correctly when you're ready to proceed.

[JWClark]

The high nitrates are a false reading because you still have nitrite in the water. I wouldn't do a water change but start that skimmer. Also, feed the tank a little pinch of food everyday to build the bacterial population and then keep it.

Starting w/ dry rock only takes significantly longer to complete a cycle than w/ liverock. Also, don't run the lights during the cycle--this likely caused the algal bloom. The algal bloom likely had ripple effects, knocking out some of the bacteria due to resource competition.

Did you remove the shrimp eventually? If not, I would do a water change as you have put way too much into the tank to start--so your nitrates will end high. Just FYI, mine read 50ppm and dropped to 5-10ppm as soon as nitrite went to 0. The nitrate test kit converts nitrate to nitrite to read levels--hence, nitrite in the water leads to false nitrate readings.

[Mishri]

you did remove the shrimp once your ammonia got high enough right? (I think 1ppm is high enough, some people recommend 3ppm or even more, which I think is too high - but does depend on what you will stock and how quickly) Running the lights likely caused the algae bloom...best to leave them off if nothing in the tank needs it.

[Stephen.h]

thanks for all the replys. (yes shrimps moved)
Going to
Do a small water change 25% get the nitrates down 10 at least
Start the skimmer for its break in period
Keep the lights off

Was wondering if should add a bit of frozen mysis shrimp in a cube i have.
Was not sure when to stop ghost feeding the tank and if this would just cause more ammonia and nitrates?
Might i have killed of some bacteria by not feeding the tank a small amount of fish food?

[matt9190]

You wont kill the bacteria by not feeding, but the number of bacteria will decrease. For example, if you tend to feed a lot every day, then your bacterial load will be high (since they have plenty of food to eat). If you feed very little or barely anything at all, some bacteria will die off, but many will remain. In other words, your number of bacteria is proportional to the amount you feed.

That being said, feeding the tank small amounts until you have a bioload (fish) is not a bad thing as it will keep a functional level of biological filtration going in the tank.

[Stephen.h]

ok going to also add a small cube of frozen mysis shrimp

[Stephen.h]

will this not bring my nitite and nitrates up even more

[JWClark]

Will raise levels initially, but once the bacterial populations are there then it will have no effect--tank will then be cycled. If you don't do it now and increase those populations, you will have a spike when you actually add a fish and start feeding it--same result, only the food goes through the fish first. This spike (it's mainly ammonia you have to worry about) will stress fish and cause kidney damage.

Don't even worry about nitrates right now. You can handle that once you have the bacterial populations you need. That being said, don't throw whole cubes of mysis every day. Just a little per day. I'd divide the cube up into 4ths or something and feed that per day.