Marine tank finished cycle but.....

[maccyg]

Hi everyone,

My first ever marine tank has just completed it's fishless cycle on Saturday evening using dry rock. I have been dosing ammonia at 1ppm every day since the cycle began and now I beginning to think that may have been overkill.

As expected when I tested the water on Sunday morning ammonia was 0ppm, nitrite was 0ppm but nitrate was off the charts at 160ppm, the test sample looked like red wine! I assumed one 90% water change would be enough to bring the nitrate down but oh no.

I spent all of yesterday doing multiple 90% water changes (around 4 in total) on the tank and have only just managed to get the nitrate levels below 80ppm. I am using RO water from my LFS.

The tank is not ready for livestock yet (planning to add a clean up crew first as I have a lot of brown algae) as I still have to get the nitrate down further and I won't have an opportunity to do this for a good few days.

How do I keep the bacteria alive in the tank over the next week or so without dosing so much ammonia that I end up in the same position as I was before with sky-high nitrates? Should I just add a pinch of fishfood here and there - would that be enough to avoid the cycle crashing? I'm just paranoid that it's taken me 8 weeks to get to this point and I don't want to end up killing off all of the bacteria by not providing enough food for the bacteria.

Cheers in advance

 

[DaveK]

The 90% water changes should have taken the nitrate reading way down.

First test your RO water that your get from your LFS. This might be starting with a high nitrate reading. Second, test your water with a different brand of test kit. They sometimes go bad or are very inaccurate.

While it's rare in this day and age, test your newly mixed SW. You may have some outside source of contamination.

It is possible to test the test kit by making solutions to calibrate it. Here is one way to do it (offsite link) - https://www.plantedtank.net/forums/...83545-calibrating-test-kits-non-chemists.html

Above all don't panic.

 

[maccyg]

Thanks DaveK, appreciate the reply. Assuming the test kit is fine (I think it is accurate as I added WAY too much ammonia to the tank while it was cycling I think which is why the nitrate reading was off the scale) how would you recommend I keep the bacteria alive in the tank while I get the nitrates down and then get a clean up crew?

Should I just add a drop of ammonia to the tank every day or so to keep it ticking over?

 

[DaveK]

... Assuming the test kit is fine (I think it is accurate ...

Never ever assume your test kit is fine, especially when it comes to nitrite and nitrate. Many go bad, many are not accurate. It is very important to verify your test kit is good. Personally, I have had more than a few go bad on me.

Bacteria will tend to go dormant if there is no food, in the form of ammonia. You can add a trace if it makes you feel better, but it's not needed.

If you made four 90% water changes, you have in effect replaced all the water. As long as the new water was good, you shouldn't be getting much of a nitrate reading. Just to show you -

Lets say the water was at 1000 ppm nitrate
First 90% water change would take this down to 100
Second 90% water change would take this down to 10
Third 90% water change would take it down to 1
Fourth 90% water change would take it down to 0.1

This is why it's so important to check everything for possible problems.

 

[maccyg]

Yes that's a very good point. When I get home tonight I'll check my test kit and I still have some mixed salt water left over in one of my containers so I'll check the nitrate on that too. Appreciate your responses - thanks

 

[nanoreefing4fun]

to RS ! Great advise from Dave ^

We love pics - start a tank thread and share your tank with us !

Sounds like it has cycled... nitrates may be hard on corals, but not so much livestock, I would add your clean up crew

 

[nanoreefing4fun]

As Dave illustrated... Nitrate (NO3) reduction is directly proportional to percentage of Water Change.

 

[nanoreefing4fun]

I would...
after cuc... wait a week and see how they do... then add 1st fish (or pair) and 1st coral, then wait a month, before adding the next fish and see how they do.

 

[maccyg]

Ah ok thanks. I had read that ceriths / nerites / hermits etc couldn't tolerate nitrate levels much above 40ppm. But I think my plan this week is to leave the tank for now (currently sitting at 80ppm nitrates) and then do another big WC on Sunday at which point I'll head over to my LFS to put a CUC in.

The setup isn't massive, it's an EA Reef Pro 600s (not sure if they're available in the US) but it holds around 235 litres including sump volume but I'll put some pics up once I've got some life in it!

I'm still planning to check my test kit / saltwater tonight though just to make sure I'm getting accurate readings.

 

[Brittle star 11]

Hi I do not know why so many people start off with dry rock?

 

[nanoreefing4fun]

I love these little micro starfish !

 

[DaveK]

Hi I do not know why so many people start off with dry rock?

Dry rock is much less expensive, and since it is dry there will be no unwanted hitch hikers on the rock. On the other hand, live rock is more or less ready to go and can contain a lot of desirable life on it. Neither choice is right or wrong, it just depends on how you feel about your system.

 

[Brittle star 11]

Not all hitchhikers are bad.