[Debz87]

I bought my marine tank about a month ago, it was secondhand and is a mature tank that has been going for 3 years.
The previous owners were mixing their own saltwater using tap water and conditioners, we have since been getting RO water from our marine shop we use. We did about a 50% change 2 weeks ago as the Nitrates were reading 200 on our little colour chart, i assume this is ppm? I have tried looking for advice on the internet and was shocked to find out this is seriously dangerous for the fish at this level.
All the fish seem fine, we have had none die and also have 2 hermits and the odd snail aswell as a fair amount of live rock, i am not sure of the exact weight but we bought a piece recently that weighed 2kg and going by that i would estimate we have 16kg, we also have coral sand that is about 3 inches thick. Our tank is about 165litres approximately.
We have a cleaner wrasse, a box fish, 4 green chromis, 1 damsel, a clown fish, 1 regal tang, 1 fuzzy dwarf lion and an emperor angel, they are all juvenile.
We want to get a bigger tank eventually.
We have a clear tube in the tank which the water goes into from the skimmer (sorry i really don't know what it is called).
We cleaned off the little pad in there as it had thick black fluffy stuff on it and rubbed a bit of stress-zyme on it so will see if this makes a difference.
We have also topped up the water at the weekend by about 10 litres as we had to move the tank and took all the livestock and water etc out and we lost some water due to spillages.
The fish are all healthy, they have nothing wrong with them on close inspection, our corals seem ok too.
I have added a few drops of invertibrate feeder in the water, would this make a difference? Have only done this 3 times in 2 weeks.
Here is the results from doing a water test.
The carbonate hardness is reading 240ppm, the ph is between 7.5 and 8 whereas it was about 8.5 last week, the nitrites are at 0 but the nitrates are looking quite high, its hard to tell as the colour on the stick is different to those of the chart but i would say it is approximately 160ppm, we had reduced the nitrates to about 30ppm last week by doing the water change, how can it go up so quickly?
Our temperature is set at 28 degrees, we feed the fish 2x a day, we feed flakes in the morning and brineshrimp or krill frozen cubes in the evening with some flakes for the herbivores, is this too much?
I was under the impression they had to be fed 3 times a day from what i have read?
Our lion fish usually has 2 live shrimps too.
Please can somebody tell me if i am over reacting or if this is a big problem and offer some advice on what to do please.

[pogodzib]

Since you have 8 fish in a tank that is about 45 gallons, I'd say that your tank is already overstocked by a couple too many fish. In reef tanks, people usually only feed one small portion per day, with some people only feeding once every 2-3 days. Also, since your tank was moved about a month ago, that could have caused the substrate to be disturbed or some of your LR to have some die off which can also be increasing your nitrates quicker.

BTW - Your carbonate hardness is slightly higher than it needs to be.

BTW2 - Welcome to RB Debbie!

[Debz87]

Thanks very much for the info, so a bigger tank asap would be good then?!
How do i get the carbonate down?
We are going to clean out the internal filter tonight, we did the external when we had to move the fish and it was disgusting, the internal filter on the very odd occasion lets out a plume of bits into the water, i have seen it do this twice in a week, i assume it shouldn't do that?
So as we have that many fish, they are all under 2 inches at present what tank size would you recommend?
The current tank is 4ft by 1ft by 1.5ft.
I was thinking of looking for a 6ft by 2ft by 2ft, not sure what volume of water that holds but thought that would be enough.
I would love to go bigger than that but we live in a 1st floor flat and am a bit worried about the weight, the one we have at the moment is positioned in front of the window where i believe the metal structures of the building will be.
We wanted to get a few more fish as well, nothing that will get very big, would like to get a mandarin dragonette and a dotty back or similar.
I take it adding more live rock is a good idea? Is there also any plants that would help keep the nitrates down?
Thanks for all the advice so far!

[pogodzib]

A bigger tank wouldn't hurt, but your current tank is just fine as long as you are careful not to overfeed your fish.

Your carbonate levels will gradually go down on its own as stoney (LPS & SPS) corals grow and since the numbers aren't overly high where it will harm your corals, I'd just wait and let it drop naturally. If you are dosing any alkalinity and calcium additives, you will want to reduce the amount you are using for a little while and keep testing the water to see how quickly your levels drop.

No, the internal filter should not be spitting out plumes of anything. A dirty pump, along with the filter may be the culprit so I'd clean both when you do clean it.

A 6'x2'x2' tank holds 180 gallons of water. However, typically, you won't want to have 180 gallons of water over a floor that isn't supported from below. I'm not going to recommend a tank size since everyone has their own preferences and budgets, but from my own experiences, I do like 6' tanks since it allows more length for fish to swim back and forth. But even with that said, one of my favorite tanks is the 40 gallon breeder tank due to a longer length and shorter height.

For your future fish preferences, if you decide you want to get a fish that generally only eats live pods such as a mandarin dragonette, the tank should be at least 125 gallons with plenty of live rock so they don't run out of food and starve.

IMO, LR is one of the most valuable pieces of a reef aquarium since it helps keep nitrates down and provides hiding places for your livestock. However, a good skimmer can be almost as valuable as a decent amount of LR if you prefer the more open look.

There are many different type of "plants" that people keep to help lower nitrates. The most common one is cheatomorpha, followed by caulerpa. Either one should be kept in a refugium and not the main display tank if at all possible.